Hello, I would like to carry out a HF calculation on one atom with fractional nuclear charge, like Z = 1.5. Is that possible in PSI4? Thanks.

# Use fractional charge in calculation

Technically, yes, in that charge is a float, not an int. But practically, it’s always expected to be integer value. You can check out the frac module (https://github.com/psi4/psi4/blob/fdac37892a4c1afa95e46665400153c223dc8eb1/psi4/driver/frac.py) if, perchance, you wanted fractional electron occupation.