upf.xsd

<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="my.xsl"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">

  <!-- Definition of elements -->

  <xs:element name="UPF">
    <xs:annotation>
      <xs:documentation>Root section</xs:documentation> 
    </xs:annotation>
    <xs:complexType>
      <xs:sequence>
        <xs:element ref="PP_INFO" minOccurs="0"/>
        <xs:element ref="PP_HEADER"/>
        <xs:element ref="PP_MESH"/>
        <xs:element ref="PP_NLCC" minOccurs="0"/>
        <xs:element ref="PP_LOCAL"/>
        <xs:element ref="PP_SEMILOCAL" minOccurs="0"/>
        <xs:element ref="PP_NONLOCAL"/>
        <xs:element ref="PP_PSWFC"/>
        <xs:element ref="PP_RHOATOM"/>
        <xs:element ref="PP_PAW" minOccurs="0"/>
      </xs:sequence>
      <xs:attribute name="version" use="required" type="upf-version-string"/>
    </xs:complexType>
  </xs:element>

  <xs:element name="PP_INFO" type="xs:string">
    <xs:annotation>
      <xs:documentation>
        For human-readable data (ignored by QE).
      </xs:documentation> 
    </xs:annotation>
  </xs:element>

  <xs:element name="PP_HEADER">
    <xs:annotation>
      <xs:documentation>
        Machine-readable minimal data on the pseudopotential.
      </xs:documentation> 
    </xs:annotation>
    <xs:complexType>
      <xs:attribute name="element" use="required" type="upf-element">
        <xs:annotation>
          <xs:documentation>Element symbol</xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="generated" use="optional" type="upf-string">
        <xs:annotation>
          <xs:documentation>Software used to generate the pseudopotential
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="author" use="optional" type="upf-string"
                                                 default="anonymous">
        <xs:annotation>
          <xs:documentation>Author of pseudopotential</xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="date" use="optional">
        <xs:annotation>
          <xs:documentation>Generation date</xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="comment" use="optional" type="upf-longstring"/>

      <xs:attribute name="pseudo_type" use="required" type="upf-pseudotype">
        <xs:annotation>
          <xs:documentation>
            Pseudopotential type (not used by the software, 
            human-readable alias)
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="relativistic" use="required" type="upf-relativistic-type">
        <xs:annotation>
          <xs:documentation>
            Level of relativistic formalism used in atomic calculation
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="is_ultrasoft" use="required" type="upf-logical">
        <xs:annotation>
          <xs:documentation>
            True if pseudopotential is ultrasoft or PAW, 
            i.e. if it has augmentation/compensation charge
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="is_paw" use="required" type="upf-logical">
        <xs:annotation>
          <xs:documentation>
            True if pseudopotential is actually a PAW dataset
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="is_coulomb" use="optional" type="upf-logical" 
                    default=".false.">
        <xs:annotation>
          <xs:documentation>
            True if pseudopotential is a Coulombian 1/r potential
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="has_so" use="optional" type="upf-logical" 
                    default=".false.">
        <xs:annotation>
          <xs:documentation>
            True if spin-orbit information is present.
            In this case, the PP_SPIN_ORB section must be present.
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="has_gipaw" use="optional" type="upf-logical"
                    default=".false.">
        <xs:annotation>
          <xs:documentation>
            True if additional information for GIPAW reconstruction is
            present. In this case, the PP_GIPAW section must be present.
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="core_correction" use="required" type="upf-logical">
        <xs:annotation>
          <xs:documentation>
            True if the pseudopotential contains pseudized core charge
            for non-linear core.
            In this case, the PP_NLCC section must be present.
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="functional" use="required" type="upf-shortstring">
        <xs:annotation>
          <xs:documentation>
            Short-name for the DFT functional used.
            It can either be an alias (such as PBE, LDA) or specify in order:
            functional for exchange, functional for corellation,
            gradient correction for exchange, gradient correction for corellation.
            E.g. PBE is 'SLA PW PBX PBC'. 
            The list of short-names understood by QE is listed at the beginning
            of file Modules/functional.f90 in its source tree.
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="z_valence" use="required" type="xs:double">
        <xs:annotation>
          <xs:documentation>
            Valence charge (atomic number - core charge) in units of
            abs(electron charge). This will usually coincide with the
            number of valence electrons.
            If the pseudopotential has been generated with a charged 
            configuration, z_valence will *not* be affected, but the sum
            of the occupations will not match this value.
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="total_psenergy" use="optional" type="xs:double"
                    default="0.0">
        <xs:annotation>
          <xs:documentation>
            Pseudopotential energy of the configuration used 
            for the pseudopotential configuration (Ry)
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="wfc_cutoff" use="optional" type="xs:double"
                    default="0.0">
        <xs:annotation>
          <xs:documentation>
            Suggested plane wave cutoff (Ry)
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="rho_cutoff" use="optional" type="xs:double"
                    default="0.0">
        <xs:annotation>
          <xs:documentation>
            Suggested charge density cutoff (Ry)
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="l_max" use="required" type="xs:integer">
        <xs:annotation>
          <xs:documentation>
            Maximum angular momentum of a valence orbital.
            !!CHECK!! if the local channel has the maximum angular momentum, 
            and it is not empty, is it counted here or not? 
            Would it have any effect if it is wrong?
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="l_max_rho" use="required" type="xs:integer">
        <xs:annotation>
          <xs:documentation>
            Maximum angular momentum of atomic charge density,
            should be 2*l_max.
            !!CHECK!! same as l_max
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="l_local" use="optional" type="xs:integer">
        <xs:annotation>
          <xs:documentation>
            If local potential was generated by inversion of a norm-conserving
            wave function, then l_local is equal to the l of this channel.
            If the local potential was generated by some other means,
            e.g. smoothing the all-electron potential, then l_local &lt; 0.
            The atomic code in QE uses l_local=-1, if the smoothing was done
            with two Bessel functions (RRKJ optimized)
            and l_local=-2, of it was done with the Troullier-Martins recipe.
            Note that the local potential always has spherical symmetry.

            This attribute is actually unused in the plane-wave code
            (stored only for reconstruction purposes).
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="mesh_size" use="required" type="xs:integer">
        <xs:annotation>
          <xs:documentation>
            Number of points in the radial grid, on which potential,
            wave functions and other quantities are stored.

            Note: the number of mesh points for the potential and the 
            wave functions may in principle be different. This is not
            allowed in the UPF 2.0.1 format.
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="number_of_wfc" use="required" type="xs:integer">
        <xs:annotation>
          <xs:documentation>
            Number of wave functions stored in the file.
            These wave functions are used by QE programs only to bootstrap
            self-consistency.

            Note: In the PAW case, these are *not* the wave functions used
            for the one-center terms. They are used ONLY to generate the
            initial charge density to bootstrap the self-consistent cycle.
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="number_of_proj" use="required" type="xs:integer">
        <xs:annotation>
          <xs:documentation>
            Number of Kleinman-Bylander projectors in the pseudopotential.
            In the PAW formalism, this is also the number of wavefunctions
            used in one-center terms. Many other quantities, e.g. the number
            of augmentation channels, depend on the value of number_of_proj.
            If the pseudopotential has no projectors, number_of_proj must be
            set to zero.
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="has_wfc" use="required" type="xs:NCName">
        <xs:annotation>
          <xs:documentation>
            Deprecated??
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="paw_as_gipaw" use="required" type="xs:NCName">
        <xs:annotation>
          <xs:documentation>
            Deprecated??
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>
    </xs:complexType>
  </xs:element>

  <xs:element name="PP_MESH">
    <xs:annotation>
      <xs:documentation>
        Defines the mesh.
      </xs:documentation> 
    </xs:annotation>
    <xs:complexType>
      <xs:sequence>
        <xs:element ref="PP_R"/>
        <xs:element ref="PP_RAB"/>
      </xs:sequence>

      <xs:attribute name="dx" use="optional" type="xs:double">
        <xs:annotation>
          <xs:documentation>
            r(i) = exp ( xmin + (i-1) dx ) / zmesh i=1,mesh
            r_ab(i) = r(i) * dx
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="xmin" use="optional" type="xs:double">
        <xs:annotation>
          <xs:documentation>
            r(i) = exp ( xmin + (i-1) dx ) / zmesh i=1,mesh
            r_ab(i) = r(i) * dx
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="zmesh" use="optional" type="xs:double">
        <xs:annotation>
          <xs:documentation>
            r(i) = exp ( xmin + (i-1) dx ) / zmesh i=1,mesh
            r_ab(i) = r(i) * dx
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="mesh" use="optional" type="xs:integer">
        <xs:annotation>
          <xs:documentation>
            Deprecated. Use mesh_size in PP_HEADER instead.
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>

      <xs:attribute name="rmax" use="required" type="xs:double">
        <xs:annotation>
          <xs:documentation>
            Deprecated??
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>

    </xs:complexType>
  </xs:element>

  <xs:element name="PP_R" type="upf-data-section">
    <xs:annotation>
      <xs:documentation>
        Data section containing the radial grid,
        on which quantities such as local potential,
        wave functions, projectors and augmentation charges are sampled.
        The ith value of these quantities corresponds to the ith
        element of the radial grid.
      </xs:documentation> 
    </xs:annotation>
    <!--    <xs:complexType>
      <xs:simpleContent>
        <xs:extension base="upf-list-of-doubles">
          <xs:attribute name="type" use="required" type="xs:NCName"/>
          <xs:attribute name="size" use="required" type="xs:integer"/>
          <xs:attribute name="columns" use="required" type="xs:integer"/>
        </xs:extension>
      </xs:simpleContent>
    </xs:complexType>
-->
  </xs:element>

  <xs:element name="PP_RAB" type="upf-data-section">
    <xs:annotation>
      <xs:documentation>
        Data section containing the radial volume element.
        These attributes have been used to generate the logarithmic grid on
        which the pseudopotential is constructed.
        The expression insode the atomic code of QE is:
          r(i) = exp ( xmin + (i-1) dx ) / zmesh i=1,mesh
          r_ab(i) = r(i) * dx
        For PAW, this is the only acceptable grid (required in V_H).
        Otherwise, any kind of grid is accepted, if it can be used to compute
        a Simpson numerical integral according to the formula
          \sum_i c_i f(i)*rab(i) = \int_0^\infty f_i dr
        where c_i are alternativly 2/3 and 4/3, except c_1=c_mesh=1/3.
        f_i is a generic function, such as the atomic wave function, sampled on
        the grid r(i): f_i = f(r_i). An equivalent definition of rab is
          rab(i) = dr(x) / dx | x= i
      </xs:documentation> 
    </xs:annotation>
  </xs:element>

  <xs:element name="PP_NLCC" type="upf-data-section">
    <xs:annotation>
      <xs:documentation>
        Data section containing the pseudized core charge
        used for non-linear core correction
        sampled on the radial grid stored in PP_R.
        It is the true charge density, i.e. it will be 
        correctly integrated as
          \sum_i 4 \pi r_i^2 nlcc_i

        Ignored if core_correction is false.
      </xs:documentation> 
    </xs:annotation>
  </xs:element>

  <xs:element name="PP_LOCAL" type="upf-data-section">
    <xs:annotation>
      <xs:documentation>
        Data section containing the local potential sampled in the radial grid
        (Ry). The potential does not contain the effect of the net valence charge
        (-e2*z_valence/r_i), which will be added directly in the plane-wave code.

        Igonred if is_coulomb (PP_HEADER).
      </xs:documentation> 
    </xs:annotation>
  </xs:element>

  <xs:element name="PP_SEMILOCAL">
    <xs:annotation>
      <xs:documentation>
        Contains number_of_proj subsections PP_VNL for PPs in semilocal form.
        Not used by QE.
      </xs:documentation> 
    </xs:annotation>
    <xs:complexType>
      <xs:sequence>
        <xs:element name="PP_VNL.1" minOccurs="0" maxOccurs="1"
                    type="upf-PP_VNL.n"/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>

  <xs:complexType name="upf-PP_VNL.n">
    <xs:annotation>
      <xs:documentation>
        Contains the pseudopotential for l and j specified in the attribute
        list.
      </xs:documentation> 
    </xs:annotation>
    <xs:complexContent>
      <xs:extension base="upf-data-section">
      </xs:extension>
    </xs:complexContent>
  </xs:complexType>

  <xs:element name="PP_NONLOCAL">
    <xs:annotation>
      <xs:documentation>
        Content of this section depends on several settings in PP_HEADER.
      </xs:documentation> 
    </xs:annotation>
    <xs:complexType>
      <xs:sequence>
        <xs:element name="PP_BETA.1" minOccurs="0" maxOccurs="1"
                    type="upf-PP_BETA.n"/>
        <xs:element name="PP_BETA.2" minOccurs="0" maxOccurs="1"
                    type="upf-PP_BETA.n"/>
        <xs:element name="PP_BETA.3" minOccurs="0" maxOccurs="1"
                    type="upf-PP_BETA.n"/>
        <xs:element name="PP_BETA.4" minOccurs="0" maxOccurs="1"
                    type="upf-PP_BETA.n"/>
        <xs:element name="PP_BETA.5" minOccurs="0" maxOccurs="1"
                    type="upf-PP_BETA.n"/>
        <xs:element name="PP_BETA.6" minOccurs="0" maxOccurs="1"
                    type="upf-PP_BETA.n"/>
        <xs:element ref="PP_DIJ"/>
        <xs:element ref="PP_AUGMENTATION" minOccurs="0"/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>

  <xs:complexType name="upf-PP_BETA.n">
    <xs:annotation>
      <xs:documentation>
        Contains a Kleinman-Bylander projector sampled on the radial grid.

        If number_of_proj > 0, there must be a PP_BETA.n section for each
        n between 1 and number_of_proj.
      </xs:documentation> 
    </xs:annotation>
    <xs:complexContent>
      <xs:extension base="upf-data-section">
        <xs:attribute name="index" use="optional" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              For PP_BETA.n, this is just n.
              
              TODO do away with the PP_BETA.n naming scheme.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="angular_momentum" use="required" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              The angular momentum of the projector.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="cutoff_radius_index" use="optional" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              The projector is assumed to be zero beyond this point.
              If it is not specified, it is assumed to be equal to the mesh size.
              
              NOTE: Not specifying cutoff_radius can introduce a considerable
              numerical noise in some integrals, especially in the PAW case.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="cutoff_radius" use="optional" type="xs:double">
          <xs:annotation>
            <xs:documentation>
              The value of the radial mesh point corresponding to cutoff_radius_index.
              This value is currently unused in the plane-wave code.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="norm_conserving_radius" use="optional" type="xs:double">
          <xs:annotation>
            <xs:documentation>
              Value of norm conserving wave function used to generate the 
              ultrasoft pseudopotential. 
              Ununsed in the code, stored only for reconstruction purposes,
              meaningless for PAW.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="ultrasoft_cutoff_radius" use="required" type="xs:double">
          <xs:annotation>
            <xs:documentation>
              UNDOCUMENTED
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="label" use="required" type="xs:NMTOKEN">
          <xs:annotation>
            <xs:documentation>
              UNDOCUMENTED
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
      </xs:extension>
    </xs:complexContent>
  </xs:complexType>

    <xs:element name="PP_DIJ">
      <xs:annotation>
        <xs:documentation>
          Hamiltonian pseudo coefficients as defined in the Vanderbilt paper
          (PRB 1990).
          If the pseudopotential is a PAW data set, they must contain the
          kinetic energy difference as well.

          !!CHECK!! a better/more accurate definition for these would be useful.
        </xs:documentation> 
      </xs:annotation>
      <xs:complexType>
        <xs:simpleContent>
          <xs:extension base="xs:double">
            <xs:attribute name="columns" use="required" type="xs:integer"/>
            <xs:attribute name="size" use="required" type="xs:integer"/>
            <xs:attribute name="type" use="required" type="xs:NCName"/>
          </xs:extension>
        </xs:simpleContent>
      </xs:complexType>
    </xs:element>


 <xs:element name="PP_AUGMENTATION">
    <xs:annotation>
      <xs:documentation>
        Compulsory for pseudopotentials with augmentation charge,
        i.e. when the pseudopotential is_ultrasoft
        (presently ultrasoft or PAW).
      </xs:documentation> 
    </xs:annotation>
    <xs:complexType>
      <xs:sequence>
        <xs:element ref="PP_Q"/>
        <xs:element ref="PP_MULTIPOLES"/>
        <xs:element ref="PP_QFCOEFF"/>
        <xs:element ref="PP_RINNER"/>
        <xs:element name="PP_QIJL.1.1.0" minOccurs="0" maxOccurs="1"
                    type="upf-PP_QIJL.n.n.n"/>
      </xs:sequence>
      <xs:attribute name="q_with_l" use="required" type="upf-logical">
          <xs:annotation>
            <xs:documentation>
              If true, the augmentation charge can depend on the value
              of the angular momentum. I.e. if a certain channel has more
              than one angular momentum component, there shall be a different
              radial form of the augmentation for each component.

             This attribute is false for Vanderbilt's original recipe.
             It is true for PAW.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
      <xs:attribute name="nqf" use="optional" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              Specifies the number of coefficients used to analytically expand
              the augmentation charge at small radius,
              according to Vanderbilt's recipe.

              Note: The analytical expansion of augmentation charge is 
              currently not implemented for PAW.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
      <xs:attribute name="nqlc" use="optional" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              Specifies the number of angular momentum components that can be
              present in the charge density, when the maximum angular momentum
              for wave functions is l_max (default: nqlc = 2*l_max+1).
 
              If nqf &gt; 0, nqlc is the dimension of several arrays.
              If nqf = 0, nqlc is not used.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
      <xs:attribute name="shape" use="optional" type="upf-shortstring">
          <xs:annotation>
            <xs:documentation>
              Describes the kind of pseudization used for the augmentation
              function. Currently unused, stored only for reconstructio purpose.

              Note: If the analytical overlap for PAW augmentation charge
              (as defined by Bloechl) will ever be implemented, this field
              will become necessary.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
      <xs:attribute name="iraug" use="optional" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              All augmentation charge must be zero beyond this point.
              Used only for PAW and only if it is greater than cutoff_radius
              for all projectors.

              If not specified, iraug is set to mesh size.
              This default works, but can generate numerical noise in some
              integrals. In order to avoid large round-off errors in 
              cancellation of PAW terms, it is important to set this paramter
              as small as possible, i.e. just outside the augmentation radius.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
      <xs:attribute name="raug" use="optional" type="xs:double">
          <xs:annotation>
            <xs:documentation>
              The value of the radial mesh point corresponding to iraug.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
      <xs:attribute name="augmentation_epsilon" use="optional" type="xs:double">
          <xs:annotation>
            <xs:documentation>
              If augmentation_epsilon &gt; 0, augmentation functions,
              whose norm is less than augmentation_epsilon will be 
              considered zero.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
      <xs:attribute name="cutoff_r" use="optional" type="xs:double">
          <xs:annotation>
            <xs:documentation>
              Deprecated?
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
      <xs:attribute name="cutoff_r_index" use="optional" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              Deprecated?
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
      <xs:attribute name="l_max_aug" use="optional" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              Deprecated?
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
    </xs:complexType>
  </xs:element>

  <xs:element name="PP_Q" type="upf-data-section">
    <xs:annotation>
      <xs:documentation>
        The norm of the augmentation functions.

        Note: The fact that Q is zero for a certain augmentation function
        does not guarantee that the function will be identically zero.
        This was erroneously assumed in UPF 2.0.0, causing small errors
        in specific cases.
      </xs:documentation> 
    </xs:annotation>
  </xs:element>

  <xs:element name="PP_MULTIPOLES" type="upf-data-section">
    <xs:annotation>
      <xs:documentation>
        The electrostatic multipoles of the corresponding augmentation channel.
        If the absolute value of a multipole is less than augmentation_epsilon,
        the corresponding function will be considered zero.

        Note: This section is compulsory for PAW and ignored otherwise.
      </xs:documentation> 
    </xs:annotation>
  </xs:element>

  <xs:element name="PP_QFCOEFF" type="upf-data-section">
    <xs:annotation>
      <xs:documentation>
        The coefficient used to perform a Taylor expansion of the augmentation
        functions at small radii.

        Note: Compulsory if nqf &gt; 0, ignored otherwise.
      </xs:documentation> 
    </xs:annotation>
  </xs:element>

  <xs:element name="PP_RINNER" type="upf-data-section">
    <xs:annotation>
      <xs:documentation>
        The radius before which the augmentation functions are expanded in a
        Taylor series.
      </xs:documentation> 
    </xs:annotation>
  </xs:element>

  <xs:complexType name="upf-PP_QIJL.n.n.n">
    <xs:annotation>
      <xs:documentation>
        If q_with_l is true, there needs to be one PP_Q.i.j.l section
        for each i and j from 1 to number_of_proj and l from 0 to l_max_rho.
        If q_with_l is false, there needs to be one PP_Q.i.j section
        for each i and j from 1 to number_of_proj.

        An augmentation function can be omitted (or replaced with an empty
        section of the same name), if at least one of the following conditions
        is met:
         
          - It is identically zero. In this case, an empty section must be 
            present (see is_null).
          - j &lt; i (Q_ij = Q_ji due to symmetry).
          - The pseudo is of PAW type and the corresponding multipole
            (PP_MULTIPOLES) is zero or less than augmentation_epsilon
          - q_with_l is true and l is *not* taken from the list
            abs(l_i-l_j), abs(l_i-l_j)+2 ... l_i+l_j-2, l_i+l_j .

        Unnecessary sections with augmentation charges are ignored.
      </xs:documentation> 
    </xs:annotation>
    <xs:complexContent>
      <xs:extension base="upf-data-section">
        <xs:attribute name="angular_momentum" use="required" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              To be documented.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="first_index" use="optional" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              The index i of the function.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="second_index" use="optional" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              The index j of the function.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="composite_index" use="optional" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              A composite index k = j*(J-1)/2 + i, 
              used internally to save memory.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="is_null" use="optional" type="upf-logical">
          <xs:annotation>
            <xs:documentation>
              If an augmentation function is identically zero,
              the data section can be replaced by an empty section
              that is_null.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
      </xs:extension>
    </xs:complexContent>
  </xs:complexType>



    <xs:element name="PP_PSWFC">
      <xs:annotation>
        <xs:documentation>
          Contains number_of_wfc data sections of the radial sample of an atomic
          wave function. These wave functions are used to set up the initial
          wave functions for the self-consistent calculation.
        </xs:documentation> 
      </xs:annotation>
      <xs:complexType>
        <xs:sequence>
          <xs:element name="PP_CHI.1" minOccurs="0" maxOccurs="1"
                      type="upf-PP_CHI.n"/>
          <xs:element name="PP_CHI.2" minOccurs="0" maxOccurs="1"
                      type="upf-PP_CHI.n"/>
        </xs:sequence>
      </xs:complexType>
    </xs:element>

  <xs:complexType name="upf-PP_CHI.n">
    <xs:annotation>
      <xs:documentation>
        An atomic wave function sampled on the radial grid.
        They are use in QE as initial conditions for the self-consistent
        calculation.

        Note: There is no link between these wave functions and the beta
        projectors in PP_NONLOCAL. number_of_wfc can be different from
        number_of_proj. 
        This quantity is stored multiplied by a factor r.
      </xs:documentation> 
    </xs:annotation>
    <xs:complexContent>
      <xs:extension base="upf-data-section">
        <xs:attribute name="l" use="required" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              Angular momentum of the wave function.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="occupation" use="required" type="xs:double">
          <xs:annotation>
            <xs:documentation>
              Occupation of the wave function in the reference configuration.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="index" use="optional" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              The index n in PP_CHI.n
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="label" use="optional" type="upf-nl-label">
          <xs:annotation>
            <xs:documentation>
              A conventional label, such as '2S', '3P', etc.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="n" use="optional" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              Pseudo-principal quantum number. 
              Usually set to l-1. Only stored for reconstruction purposes.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="pseudo_energy" use="optional" type="xs:double">
          <xs:annotation>
            <xs:documentation>
              Single-particle energy of the wave function in atomic 
              configuration.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="cutoff_radius" use="optional" type="xs:double">
          <xs:annotation>
            <xs:documentation>
              Inner norm-conserving radius used by atomic code in QE.
              Only stored for reconstruction purposes.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="ultrasoft_cutoff_radius" use="optional" 
                      type="xs:double">
          <xs:annotation>
            <xs:documentation>
              Outer ultrasoft radius used by atomic code in QE.
              Only stored for reconstruction purposes.
              A conventional label, such as '2S', '3P', etc.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
      </xs:extension>
    </xs:complexContent>
    </xs:complexType>

    <xs:element name="PP_RHOATOM" type="upf-data-section">
      <xs:annotation>
        <xs:documentation>
          The valence charge density in the reference atomic configuration.
          Can be used to genreate the initial charge density in the
          self-consistent calculation.

          This quantity is stored multiplied by a factor of r^2.
        </xs:documentation> 
      </xs:annotation>
    </xs:element>

    <xs:element name="PP_SPIN_ORB">
      <xs:annotation>
        <xs:documentation>
          Contains additional information required to perform 
          self consistent calculations with spin-orbit coupling.

          The section must be present if 'has_so' in section
          PP_HEADER is true.  Otherwise it is ignored.
        </xs:documentation> 
      </xs:annotation>
      <xs:complexType>
        <xs:sequence>
          <xs:element name="PP_RELWFC.1" minOccurs="0" maxOccurs="1"
                      type="upf-PP_RELWFC.n"/>
          <xs:element name="PP_RELBETA.1" minOccurs="0" maxOccurs="1"
                      type="upf-PP_RELBETA.n"/>
        </xs:sequence>
      </xs:complexType>
  </xs:element>

  <xs:complexType name="upf-PP_RELWFC.n">
    <xs:annotation>
      <xs:documentation>
        Contains data necessary to perform a spin-orbit self-consistent
        calculation.

        For each wave function stored in the PP_PSWFC section,
        there must be one empty section of this kind.
        The index n runs from 1 to number_of_wfc.
      </xs:documentation> 
    </xs:annotation>
    <xs:complexContent>
      <xs:extension base="upf-data-section">
        <xs:attribute name="jchi" use="required" type="xs:double">
          <xs:annotation>
            <xs:documentation>
              Total angular momentum of the wave function,
              i.e. l+1/2, l-1/2 when l>0.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="index" use="optional" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              The index n in PP_RELWFC.n
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="els" use="optional" type="upf-nl-label">
          <xs:annotation>
            <xs:documentation>
              A conventional label for the wave function, 
              such as '2S', '3P', etc.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="nn" use="optional" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              The actual principal quantum number.
              Note: This can differ from the pseudo-principal quantum number
              stored in the 'nchi' attribute of PP_CHI.n
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="lchi" use="optional" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              See attribute 'lchi' of PP_CHI.n (which is used as default).
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="oc" use="optional" type="xs:double">
          <xs:annotation>
            <xs:documentation>
              See attribute 'occupations' of PP_CHI.n
              (which is used as default).
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
      </xs:extension>
    </xs:complexContent>
  </xs:complexType>

  <xs:complexType name="upf-PP_RELBETA.n">
    <xs:annotation>
      <xs:documentation>
        Contains data necessary to perform a spin-orbit self-consistent
        calculation.

        For each projector in section PP_NONLOCAL,
        there must be one empty section of this kind.
        The index n runs from 1 to number_of_proj.
      </xs:documentation> 
    </xs:annotation>
    <xs:complexContent>
      <xs:extension base="upf-data-section">
        <xs:attribute name="index" use="optional" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              The index n in PP_RELBETA.n
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="jjj" use="required" type="xs:double">
          <xs:annotation>
            <xs:documentation>
              Total angular momentum of the wave function.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="lll" use="optional" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              See attribute 'angular_momentum' or corresponding PP_BETA.n
              subsection of PP_NONLOCAL (whose value is used as default).
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
      </xs:extension>
    </xs:complexContent>
  </xs:complexType>

  <xs:element name="PP_PAW">
    <xs:annotation>
      <xs:documentation>
        Contains additional information required to perform 
        projector-augmented self-consistent calculation,
        i.e. an all-electron wave function for each projector,
        the all-electron local potential as well as the all-electron
        core charge for non-linear core correction.

        The section (as well as PP_MULTIPOLES and PP_NONLOCAL) must be present
        if 'is_paw' in section PP_HEADER is true.  Otherwise it is ignored.
      </xs:documentation> 
    </xs:annotation>
    <xs:complexType>
      <xs:sequence>
        <xs:element ref="PP_OCCUPATIONS"/>
        <xs:element ref="PP_AE_NLCC"/>
        <xs:element ref="PP_AE_VLOC"/>
        <xs:element name="PP_AEWFC.1" minOccurs="0" maxOccurs="1"
                    type="upf-PP_AEWFC.n"/>
        <xs:element name="PP_PSWFC.1" minOccurs="0" maxOccurs="1"
                    type="upf-PP_PSWFC.n"/>
      </xs:sequence>
      <xs:attribute name="core_energy" use="optional" type="xs:double"
                    default="0.0">
        <xs:annotation>
          <xs:documentation>
            Constant that has to be added to the valence energy in order to
            obtain the all-electron energy.
            As it is a constant, it has no effect on the result
            of the calculation.

            Only used, if all atoms of the system are described by
            PAW data sets.
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute> 

      <xs:attribute name="paw_data_format" use="required" type="xs:integer">
        <xs:annotation>
          <xs:documentation>
            UNDOCUMENTED
            
            See gipaw_data_format of PP_GIPAW section.
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute> 

    </xs:complexType>
  </xs:element>

  <xs:element name="PP_OCCUPATIONS" type="upf-data-section">
    <xs:annotation>
      <xs:documentation>
        Occupations used in the atomic reference configuration.
        
        Note: For higher energy projectors, this occupation will
        typically be zero. They are used as an initial condition for the
        self-consistency of the terms
          
          \rho_{ij} = \sum_b f_b \langle \beta_i | \psi_b \rangle
                                 \langle \psi_b | \beta_j \rangle

        Dimensions: number_of_proj 
      </xs:documentation> 
    </xs:annotation>
  </xs:element>

  <xs:element name="PP_AE_NLCC" type="upf-data-section">
    <xs:annotation>
      <xs:documentation>
        The all-electron core charge (no factors r^2 or 4\pi
        as in PP_NLCC).

        Note: This section must be present even when the 
        attribute 'core_correction' of section PP_HEADER is false
        in order to correctly reproduce the all-electron energy.

        Dimension: mesh_size
      </xs:documentation> 
    </xs:annotation>
  </xs:element>

  <xs:element name="PP_AE_VLOC" type="upf-data-section">
    <xs:annotation>
      <xs:documentation>
        The all-electron valence potential.

        Dimension: mesh_size
      </xs:documentation> 
    </xs:annotation>
  </xs:element>

  <xs:complexType name="upf-PP_AEWFC.n">
    <xs:annotation>
      <xs:documentation>
        Contains one all-electron orbital for each projector.

        The index n ranges from 1 to number_of_proj.

        Note: The orbitals are stored multiplied by a factor of r.
        I.e. their square module already contain the factor r^2 of
        the spherical volume element.

        Dimension: mesh_size
      </xs:documentation> 
    </xs:annotation>
    <xs:complexContent>
      <xs:extension base="upf-data-section">
        <xs:attribute name="index" use="required" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              UNDOCUMENTED

              Maybe: The index n in PP_AEWFC.n
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="l" use="required" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              UNDOCUMENTED

              Maybe: Angular momentum of the wave function.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="label" use="required" type="upf-nl-label">
          <xs:annotation>
            <xs:documentation>
              UNDOCUMENTED

              Maybe: A conventional label, such as '2S', '3P', etc.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
      </xs:extension>
    </xs:complexContent>
  </xs:complexType>

  <xs:complexType name="upf-PP_PSWFC.n">
    <xs:annotation>
      <xs:documentation>
        Contains one pseudo orbital for each projector.

        The index n ranges from 1 to number_of_proj.

        Note: The orbitals are stored multiplied by a factor of r.
        I.e. their square module already contain the factor r^2 of
        the spherical volume element.

        Dimension: mesh_size
      </xs:documentation> 
    </xs:annotation>
    <xs:complexContent>
      <xs:extension base="upf-data-section">
        <xs:attribute name="index" use="required" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              UNDOCUMENTED

              Maybe: The index n in PP_PSWFC.n
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="l" use="required" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              UNDOCUMENTED

              Maybe: Angular momentum of the wave function.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="label" use="required" type="upf-nl-label">
          <xs:annotation>
            <xs:documentation>
              UNDOCUMENTED

              Maybe: A conventional label, such as '2S', '3P', etc.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
      </xs:extension>
    </xs:complexContent>
  </xs:complexType>

  <xs:element name="PP_GIPAW_RECONSTRUCTION">
    <xs:annotation>
      <xs:documentation>
        Contains additional information required by the GIPAW code
        in order to reconstruct the all-electron charge density
        and to calculate the NMR response.

        This section must be present, if 'has_gipaw' in section PP_HEADER
        is true.

        Note: This section is independent of the PP_PAW section.
      </xs:documentation> 
    </xs:annotation>
    <xs:complexType>
      <xs:sequence>
        <xs:element ref="PP_GIPAW_CORE_ORBITALS"/>
        <xs:element ref="PP_GIPAW_ORBITALS"/>
        <xs:element ref="PP_GIPAW_VLOCAL"/>
      </xs:sequence>

      <xs:attribute name="gipaw_data_format" use="required" type="xs:integer">
        <xs:annotation>
          <xs:documentation>
            Format version string composed of three dot-separated integers.
            Current version is "0.1.0".
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute> 

    </xs:complexType>
  </xs:element>

  <xs:element name="PP_GIPAW_CORE_ORBITALS">
    <xs:annotation>
      <xs:documentation>
        Contains the all-electron core orbitals.
      </xs:documentation> 
    </xs:annotation>
    <xs:complexType>
      <xs:sequence>
        <xs:element name="PP_GIPAW_CORE_ORBITAL.n" minOccurs="0" maxOccurs="1"
                    type="upf-PP_AEWFC.n"/>
      </xs:sequence>
      <xs:attribute name="number_of_core_orbitals" use="required" type="xs:integer">
        <xs:annotation>
          <xs:documentation>
            The number of core orbitals included in the data set.
          </xs:documentation> 
        </xs:annotation>
      </xs:attribute>
    </xs:complexType>
  </xs:element>

  <xs:complexType name="upf-GIPAW_CORE_ORBITAL.n">
    <xs:annotation>
      <xs:documentation>
        Contains all-electron orbital for particular projector.

        The index n ranges from 1 to number_of_proj.

        Note: The orbitals are stored multiplied by a factor of r.
        I.e. their square module already contain the factor r^2 of
        the spherical volume element.

        Dimension: mesh_size
      </xs:documentation> 
    </xs:annotation>
    <xs:complexContent>
      <xs:extension base="upf-data-section">
        <xs:attribute name="index" use="optional" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              UNDOCUMENTED

              The index n in PP_GIPAW_CORE_ORBITAL.n
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="l" use="required" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              Angular momentum quantum number of the wave function.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="n" use="required" type="xs:integer">
          <xs:annotation>
            <xs:documentation>
              Principal quantum number of the wave function.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="label" use="required" type="upf-nl-label">
          <xs:annotation>
            <xs:documentation>
              A conventional label for the wave function, 
              such as '2S', '3P', etc.
            </xs:documentation> 
          </xs:annotation>
        </xs:attribute>
      </xs:extension>
    </xs:complexContent>
  </xs:complexType>

  <xs:element name="PP_GIPAW_ORBITALS">
    <xs:annotation>
      <xs:documentation>
        Contains the valence pseudo and all-electron orbitals.
      </xs:documentation> 
    </xs:annotation>
    <xs:complexType>
      <xs:sequence>
        <xs:element name="PP_GIPAW_ORBITAL.n" minOccurs="0" maxOccurs="1"
                    type="upf-PP_AEWFC.n"/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>

  <xs:complexType name="upf-GIPAW_ORBITAL.n">
    <xs:annotation>
      <xs:documentation>
        Contains all-electron orbital for particular projector.

        The index n ranges from 1 to number_of_proj.

        Note: The orbitals are stored multiplied by a factor of r.
        I.e. their square module already contain the factor r^2 of
        the spherical volume element.

        Dimension: mesh_size
      </xs:documentation> 
    </xs:annotation>
     <xs:sequence>
       <xs:element ref="PP_GIPAW_ORBITAL_AE"/>
       <xs:element ref="PP_GIPAW_ORBITAL_PS"/>
     </xs:sequence>
    <xs:attribute name="index" use="optional" type="xs:integer">
      <xs:annotation>
        <xs:documentation>
          UNDOCUMENTED

          The index n in PP_GIPAW_CORE_ORBITAL.n
        </xs:documentation> 
      </xs:annotation>
    </xs:attribute>
    <xs:attribute name="l" use="required" type="xs:integer">
      <xs:annotation>
        <xs:documentation>
          Angular momentum quantum number of the wave function.
        </xs:documentation> 
      </xs:annotation>
    </xs:attribute>
    <xs:attribute name="n" use="required" type="xs:integer">
      <xs:annotation>
        <xs:documentation>
          Principal quantum number of the wave function.
        </xs:documentation> 
      </xs:annotation>
    </xs:attribute>
    <xs:attribute name="label" use="required" type="upf-nl-label">
      <xs:annotation>
        <xs:documentation>
          A conventional label for the wave function, 
          such as '2S', '3P', etc.
        </xs:documentation> 
      </xs:annotation>
    </xs:attribute>
    <xs:attribute name="cutoff_radius" use="required" type="xs:double">
      <xs:annotation>
        <xs:documentation>
          Inner norm-conserving cutoff radius.
          Used as core radius by the GIPAW code.
        </xs:documentation> 
      </xs:annotation>
    </xs:attribute>
    <xs:attribute name="ultrasoft_cutoff_radius" use="optional" type="xs:double">
      <xs:annotation>
        <xs:documentation>
          Outer ultra-soft cutoff radius.
        </xs:documentation> 
      </xs:annotation>
    </xs:attribute>
  </xs:complexType>

  <xs:element name="PP_GIPAW_ORBITAL_AE" type="upf-data-section">
    <xs:annotation>
      <xs:documentation>
        Contains all-electron valence orbital.

        Note: The orbitals are stored multiplied by a factor of r.
        I.e. their square module already contain the factor r^2 of
        the spherical volume element.
      </xs:documentation> 
    </xs:annotation>
  </xs:element>

  <xs:element name="PP_GIPAW_ORBITAL_PS" type="upf-data-section">
    <xs:annotation>
      <xs:documentation>
        Contains pseudo valence orbital.

        Note: The orbitals are stored multiplied by a factor of r.
        I.e. their square module already contain the factor r^2 of
        the spherical volume element.
      </xs:documentation> 
    </xs:annotation>
  </xs:element>

  <xs:element name="PP_GIPAW_VLOCAL">
    <xs:annotation>
      <xs:documentation>
        Contains the valence pseudo and all-electron orbitals.
      </xs:documentation> 
    </xs:annotation>
    <xs:complexType>
      <xs:sequence>
        <xs:element ref="PP_GIPAW_VLOCAL_AE"/>
        <xs:element ref="PP_GIPAW_VLOCAL_PS"/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>

  <xs:element name="PP_GIPAW_VLOCAL_PS" type="upf-data-section">
    <xs:annotation>
      <xs:documentation>
        Contains pseudo local potential corresponding to GIPAW orbitals.

        Note: The potential is stored multiplied by a factor of r
              (different from PP_VLOC).
      </xs:documentation> 
    </xs:annotation>
  </xs:element>

  <xs:element name="PP_GIPAW_VLOCAL_AE" type="upf-data-section">
    <xs:annotation>
      <xs:documentation>
        Contains all-electron local potential corresponding to GIPAW orbitals.

        Note: The potential is stored multiplied by a factor of r
              (different from PP_VLOC).
      </xs:documentation> 
    </xs:annotation>
  </xs:element>

  <!-- User-defined types -->

  <xs:simpleType name="upf-version-string">
    <xs:restriction base="xs:string">
      <xs:maxLength value="14"/>
      <xs:pattern value="[0-9\.]+"/>
    </xs:restriction>
  </xs:simpleType>

  <xs:simpleType name="upf-element">
    <xs:restriction base="xs:string">
      <xs:maxLength value="2"/>
      <xs:pattern value="[A-Za-z]+"/>
      <xs:whiteSpace value="collapse"/>
    </xs:restriction>
  </xs:simpleType>
 
  <xs:simpleType name="upf-string">
    <xs:restriction base="xs:string">
      <xs:maxLength value="80"/>
    </xs:restriction>
  </xs:simpleType>

  <xs:simpleType name="upf-longstring">
    <xs:restriction base="xs:string">
      <xs:maxLength value="200"/>
    </xs:restriction>
  </xs:simpleType>

  <xs:simpleType name="upf-shortstring">
    <xs:restriction base="xs:string">
      <xs:maxLength value="20"/>
    </xs:restriction>
  </xs:simpleType>

  <xs:simpleType name="upf-nl-label">
    <xs:restriction base="xs:string">
      <xs:maxLength value="2"/>
    </xs:restriction>
  </xs:simpleType>

  <xs:simpleType name="upf-pseudotype">
    <xs:restriction base="xs:string">
      <xs:enumeration value="NC">
        <xs:annotation>
          <xs:documentation>norm-conserving</xs:documentation> 
        </xs:annotation>
      </xs:enumeration>
      <xs:enumeration value="SL">
        <xs:annotation>
          <xs:documentation>norm-conserving (semi-local form)
          </xs:documentation> 
        </xs:annotation>
      </xs:enumeration>
      <xs:enumeration value="US">
        <xs:annotation>
          <xs:documentation>Vanderbilt's ultrasoft</xs:documentation> 
        </xs:annotation>
      </xs:enumeration>
      <xs:enumeration value="PAW">
        <xs:annotation>
          <xs:documentation>Projector-Augmented Wave</xs:documentation> 
        </xs:annotation>
      </xs:enumeration>
      <xs:enumeration value="1/r">
        <xs:annotation>
            <xs:documentation>Coulombian 1/r potential</xs:documentation> 
        </xs:annotation>
      </xs:enumeration>
    </xs:restriction>
  </xs:simpleType>

  <xs:simpleType name="upf-relativistic-type">
    <xs:restriction base="xs:string">
      <xs:enumeration value="no">
        <xs:annotation>
          <xs:documentation>non-relativistic calculation</xs:documentation> 
        </xs:annotation>
      </xs:enumeration>
      <xs:enumeration value="scalar">
        <xs:annotation>
          <xs:documentation>scalar-relativistic calculation</xs:documentation> 
        </xs:annotation>
      </xs:enumeration>
      <xs:enumeration value="full">
        <xs:annotation>
          <xs:documentation>full-relativistic calculation</xs:documentation> 
        </xs:annotation>
      </xs:enumeration>
    </xs:restriction>
  </xs:simpleType>

  <xs:simpleType name="upf-logical">
    <xs:restriction base="xs:string">
      <xs:enumeration value=".true."/>
      <xs:enumeration value="T"/>
      <xs:enumeration value=".false."/>
      <xs:enumeration value="F"/>
    </xs:restriction>
  </xs:simpleType>

  <xs:simpleType name="upf-data-type">
    <xs:restriction base="xs:string">
      <xs:enumeration value="character"/>
      <xs:enumeration value="logical"/>
      <xs:enumeration value="integer"/>
      <xs:enumeration value="real"/>
      <xs:enumeration value="complex"/>
    </xs:restriction>
  </xs:simpleType>
 
  <!-- For some reason, adding mixed="true" still doesn't allow for this
       type to be extended by a mixed="true" type. -->
  <xs:complexType name="upf-data-section">
    <xs:simpleContent>
      <xs:extension base="xs:string">
        <xs:attribute name="type" use="required" type="upf-data-type"/>
        <xs:attribute name="size" use="required" type="xs:integer"/>
        <xs:attribute name="columns" use="optional" type="xs:integer"
                      default="4"/>
      </xs:extension>
    </xs:simpleContent>
  </xs:complexType>


</xs:schema>