Re: [cclib-devel] three things

[Adam T. <a-t...@st...>]

> It looks like there are three distinct types of orbitals now: atomic
> orbitals, basis set orbitals, and molecular orbitals. Molecular orbitals
> are composed of linear combinations of basis set orbitals, which are
> composed of linear combinations of atomic orbitals (is this correct?).
> For Gaussian, basis set orbitals are equal to the atomic orbitals.

Molecular orbitals are linear combinations of basis set orbitals.
Gaussian uses atomic orbitals as the basis set orbitals. ADF uses either
atomic orbitals (no symmetry) or symmetry adapted linear combinations
(SALCs) of atomic orbitals for its basis set.

> Is there any need to store basis set orbitals in an attribute? So long
> as the ADF parser creates a mocoeffs matrix which describes the MOs in
> terms of the AOs (and not the basis set orbitals) I think we don't need
> the basis set orbitals. 

The problem is that ADF stores mocoeffs in terms of the basis set
orbitals (it calls them CFOs, or something like that). It then breaks up
these orbitals by symmetry, and prints their corresponding mocoeffs matrix.

> Regarding the aonames, to be honest, I forget why I wanted to extract
> aonames in the first place. In short, I think we should forget about
> aonames (I'll remove it from the relevant places if you agree), and
> concentrate on getting mocoeff the same between different programs.

I'd like the aonames because it's key to how PyMOlyze works. It reads
the list of aonames, and lets the user specify fragments in terms of
those. For instance, I usually create the following fragments: Mo d, Mo
s/p, S, O, C/H. Occasionally, I split up the sulfur orbitals into p and
s/d fragments.

Adam