Term symbols and Dirac

[Mhmd Al ahmad]

Dear DIRAC users,

We know that in relativistic theory neither L nor S are good quantum numbers, so one needs to project to the non-relativistic states in someway when we give the term symbols. Are there any common projectors to non-relativistic states? i.e. when S, L are quasi good quantum numbers I can still describe the state by term symbols .... , so can Dirac take that into consideration in its output file?

Best regards,

Mohamed.

[Visscher, L. (Luuk)]

Dear Mohamed,

We do not have this functionality and it would also not be straightforward to implement as we typically only compute the relativistic wave functions. Defining projectors would imply that we also need to compute the non-relativistic states and that the representation of both needs to be compatible. 

Especially the latter condition is tricky, given our current code base, I think.

As our code is open source, anyone interested may try to develop this, but I am afraid it will be a non-trivial coding exercise.

best regards,

Luuk

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[Hans Jørgen Aagaard Jensen]

For some models you can ask for expectation values of Lx, Ly, Lz and Sx, Sy, Sz.

 

Best regards, Hans Jørgen.

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[jvi...@gmail.com]

Dear Mohamed and other Dirac users and experts,

This is something I have always been very interested in.

For SCF/DFT in linear symmetry, I use Mulliken population analysis and for each open shell, or any frontier orbital, I analyze amount in "alpha" or "beta", this in combination with the m_j value gives a breakdown of orbital character to "sigma+pi", "pi+delta", "delta+phi", etc.

Then, from *RESOLVE output, one can see which determinants have which orbitals occupied, so an approximate M_s could be estimated and, similarly, the Lambda in combination with the above.

Post-SCF/DFT computations could be harder. But KRCI does have .OMEGAQ, so this could work.

Best regards,

Jakub

Dne neděle 29. prosince 2024 v 10:32:24 UTC+1 uživatel h...@sdu.dk napsal: