Re: [cclib-devel] Forces from gaussian job (added feature)

[Hugh Chaffey-M. <hug...@ch...>]

Hi Karol

> Could I also look over your code and input/output example?

Sure, I'll send these in a separate email to you only, since Noel has it 
already.

> Z-matrix parsing and/or interconversion with cartesians would be useful...
> currently I do it on a regular basis with openbabel. If not parsed, perhaps
> a helper method could build and return the z-matrix via openbabel.

That would surely be useful. Coul I quickly ask, do you use the C++ API 
directly when doing this or do you mean you convert between file formats with 
z-matrix/cartesian specifications?

> For derived quantities like (second) derivatives, it will be harder to
> maintain clarity and consistency between outputs from various programs if
> we were to provide them potentially in both cartesian and internal
> coordinates. I would again suggest a helper method in this case that
> converts the standard cartesian form to internal coordinates, with a
> Z-matrix or atom ordering given as input.

Yep I suppose that would be good. When gradients are already available in 
terms of the z-matrix, I would have thought it incurs unnecessary complexity 
to invoke other methods to convert the gradients from cartesians to z-matrix. 
But in general, such infrastructure in the code would be useful.

In a related project I'm currently working on, I have already written code to 
convert from forces in cartesians to forces in z-matrix, and it numerically 
differentiates the function Z(C) that returns z-matrix coordinates, Z, in 
terms of the cartesians, C, and implements the function Z using the python 
interface to openbabel.

> > As I may have mentioned, I will probably add support for a number of
> > other programs, such as GAMESS, NWChem and possibly VASP, at some point,
> > so obviously should do this in a style that is consistent with the rest
> > of cclib.
>
> We don't parse nwchem or VASP output files at the moment, so there is no
> parse to currently add code to for those programs.

Well if I were to write some code to parse them, would you want to add it to 
cclib?

Cheers
Hugh