Regarding manually addition the contraction coefficients in dyall basis in Dirac format

[bala...@gmail.com]

Dear all,

I am seeking for you help to manually add the contraction coefficients for Dyall basis in Dirac.

Example Be atom in dz basis in non zero spin, has separate contraction coefficients for 2p+, 2p- corresponding to same exponents. But in dirac, there's only one set of exponents for s type functions, p type functions and so on. What format should we follow to manually enter the coefficients in Dirac software?

Thanks in advance!

Regards,

Renu

[Trond SAUE]

Dear Renu,

DIRAC uses a scalar basis set, as you can see here

https://doi.org/10.1063/5.0004844

This means that at the AO-integral-level, DIRAC can for instance not distinguish p1/2 and p3/2 functions and so you can not give separate sets of contraction coefficients. I have plan on possibly changing that. On the other hand, contraction is more problematic with spin-orbit interaction. Suppose that you calculate some property of some molecules AX, where X are elements of the same column in the periodic table. For the heavy elements p1/2 and p3/2 are truly different and would require distinct contraction coefficients. However, for the lightest elements separate contraction coeffcients for p1/2 and p3/2 would lead to linear dependency since the orbitals are very similar.

All the best,

   Trond

--

Trond Saue
Laboratoire de Chimie et Physique Quantiques
UMR 5626 CNRS --- Université Toulouse III-Paul Sabatier
118 route de Narbonne, F-31062 Toulouse, France

Phone : +33/561556361 Fax: +33/561556065
Mail : trond...@irsamc.ups-tlse.fr
Web : https://dirac.ups-tlse.fr/saue
DIRAC : http://www.diracprogram.org/
ESQC : http://www.esqc.org/
ERC Advanced Grant: HAMP-vQED

Book: Principles and Practices of Molecular Properties: Theory, Modeling, and Simulations

[bala...@gmail.com]

Dear Prof. Trond,

Thank you for your reply.

Regards,

Renu