[DFTB-Plus-User] Requesting additional accessor functions in the DFTB+ api (or libdftb+)

[Bálint Aradi]

Dear Nitant,

> I am grateful for the inclusion of the api in the new release of
> dftb+ (19.1).

Thanks a lot, I am happy to hear, that you find the API useful.

> -> dftbp_get_stress_tensor(): to obtain stress tensor
> 
> -> dftbp_get_coords_and_lattice_vecs(): to obtain the current 
> coordinates and lattice vectors.

None of the should be major difficulty. Could you make a feature request
(issue) on GitHub listing this two items? Then it's easier to keep track
of it.

> -> I noticed that during the use of the api, if I specify 
> WriteResultsTag = Yes in the Options block, I still see no output 
> written to results.tag. Is this intended? -> As I noted above,
> exclusively specifying the Driver block has no effect on the
> calculation which is always static. I was wondering if there are any
> plans to upgrade this functionality, to also allow access to
> coordinates after geometry optimization?

Yes, results.tag is not written as the current API basically accesses
the processGeometry() subroutine

https://github.com/dftbplus/dftbplus/blob/d47fa91e38c1528eb4aec11c60cc062aeda24265/prog/dftb%2B/lib_dftbplus/main.F90#L328

but results.tag is written outside of it. For the same reason, the
Driver {} block is completely ignored, as the idea is that the
simulationion is driven from outside (e.g. by an MM-code).

Could you eventually tell us more about the use case, where you think an
internal geometry optimization triggered via the API could be useful?
One may implement this, but that would require some code reorganization,
so may not be entirely trivial.

Best regards,

Bálint


-- 
Dr. Bálint Aradi
Bremen Center for Computational Materials Science, University of Bremen
http://www.bccms.uni-bremen.de/cms/people/b-aradi/


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