Change Molecule.nelec to the total number of electrons

[chmwzc]

This was done in response to feedback on Qibochem from my Dec 2023 RAP attachment students.

First, they asked what's .nso and .nelec: Documentation for these class attributes was missing.
Follow-up question: why are all the .n* attributes integers, except for .nelec, which is currently (nalpha, nbeta)?

Hence, I changed .nelec to the total number of electrons directly.

Also: Added documentation for some other Molecule class attributes that are potentially useful.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (2718de5) 100.00% compared to head (ff9aaeb) 100.00%.
Report is 15 commits behind head on main.

Additional details and impacted files

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  Coverage   100.00%   100.00%           
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  Files           11        11           
  Lines          401       402    +1     
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+ Hits           401       402    +1     

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unittests	100.00% <100.00%> (ø)

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[damarkian]

This was done in response to feedback on Qibochem from my Dec 2023 RAP attachment students.

First, they asked what's .nso and .nelec: Documentation for these class attributes was missing. Follow-up question: why are all the .n* attributes integers, except for .nelec, which is currently (nalpha, nbeta)?

Hence, I changed .nelec to the total number of electrons directly.

Also: Added documentation for some other Molecule class attributes that are potentially useful.

.nelec is a tuple because pyscf made it so. It was just carried over.

I agree that it can be confusing. If we just use .nelec as the number of electrons, then we have to be careful that it remains so, and not overlap into .nso, which is the number of electrons in the active space.

Looks ok to me now.