Fortran Simulation DPD

DPD program

For the dpd example, we recommend generating an initial configuration using the initialize program, with namelist input similar to the following

&nml n = 100, density = 3.0, lattice = .false.,
velocities = .true., soft=.true. /

The above value of the density is typical when using this method to model water.

For testing we compare with an approximate DPD equation of state for P

• RD Groot, PB Warren, J Chem Phys, 107, 4423 (1997),
• TP Liyana-Arachchi, SN Jamadagni, D Eike, PH Koenig, JI Siepmann, J Chem Phys, 142, 044902 (2015).

The paper of Liyana-Arachchi et al (2015) gives an improvement of the original EOS of Groot and Warren (1997), which is more accurate and applicable over a wider range of state points. The function is included in the dpd program, and the expected value of P (labelled EOS below) is printed for comparison at the end. We give results obtained by both the Lowe thermostat (L) and the Shardlow algorithm (S). We take the default values of a ρ/T=75, and of other parameters not mentioned below.

T	ρ	P (EOS)	P (L)	P (S)
0.5	3.0	11.864	11.814(2)	11.819(2)
1.0	3.0	23.587	23.637(2)	23.635(2)
1.5	3.0	35.276	35.449(3)	35.455(4)
2.0	3.0	46.951	47.257(4)	47.265(5)
1.0	2.0	14.187	14.320(2)	14.316(2)
1.0	4.0	32.811	32.622(3)	32.628(3)
1.0	5.0	41.887	41.539(4)	41.533(3)