PySCF theory - Spin orbit coupling

[mljchen102]

Is it possible to include spin-orbit coupling as one of the parameters for the pyscftheory function? I'd like to use it with HF, DFT, CCSD(T), and multiconfigurational methods (CASSCF)

[RagnarB83]

It could probably be enabled. Can you show me an example of the recommended way of doing it in pyscf in general ?

[mljchen102]

This is an example for HF, probably similar for DFT: https://github.com/pyscf/pyscf/blob/master/examples/scf/44-soc_ecp.py
For CCSD: https://github.com/pyscf/pyscf/blob/master/examples/cc/03-gccsd.py
I don't think SOC is implemented for CASSCF in PySCF right now

[RagnarB83]

OK I have changed the pySCFTheory behaviour so that if you simultaneusly enable GHF or GKS and x2C then non-collinear spin-orbit coupling should be enabled. See updated NEW branch.

theory = PySCFTheory(scf_type="GKS", basis="def2-SVP", functional="BLYP",
            x2c=True)

For CCSD I don't know, I get an assertion error even when running the GCCSD example with the latest pySCF.

[mljchen102]

You have to pip install git+https://github.com/pyscf/pyscf for the GCCSD part to work. I believe they updated the GCCSD part in the repository after the most recent 2.13.1 release

[RagnarB83]

Gotcha, well then it should work and will probably test it out myself at some point.

For clarity: ASH now does the same thing as pyscf. If the reference is RHF, UHF, RKS or UKS and x2c is enabled then we get scalar relativistic x2c. If GHF/GKS then we get x2c with spin-orbit coupling.