Specify basis set as str, list, or dict
Expected Behavior
It should be possible to specify basis set in the three following ways:
MolecularSystem.set_core_region(fragments=frags, basis='basis')
MolecularSystem.set_core_region(fragments=frags, basis=['basis1', 'basis2', 'basis2'])
MolecularSystem.set_core_region(fragments=frags, basis={'O': 'basis1', 'H': 'basis2'})
The same behavior should also be allowed for basis set specifications to MolecularSystem.add_region()
.
Current Behavior
Currently only the two first options are possible, and only the first for add_region().