Is it possible to include Spin-Orbit Coupling without Scalar Relativistic effects in DIRAC?

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Mhmd Al ahmad

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Jul 21, 2026, 8:20:25 AM (11 days ago) Jul 21
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Hi DIRAC developers and users,

We can obtain results without spin-orbit coupling using ".SPINFREE". Can we obtain results without scalar relativistic effects? 

Is there a way in DIRAC to perform calculations where the Hamiltonian includes only the Spin-Orbit operator acting on a non-relativistic reference state?

Any guidance or recommended input parameters would be greatly appreciated.

Best regards,
Mohamed


Hans Jørgen Aagaard Jensen

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Jul 23, 2026, 1:47:32 PM (8 days ago) Jul 23
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Hi

Yes, you can obtain non-relativistic results in Dirac without both scalar and spin-orbit relativistic effects, for example using the Levy-Leblond model.

No, you cannot do calculations with spin-orbit and without scalar relativistic effects in Dirac. Other programs, for example Dalton, can do it approximately using the Breit-Pauli spin-orbit operator;  typical use in Dalton would be phosphorescence in molecules with only light elements (so light that scalar relativistic effects are not significant for the property of interest).

Best regards, Hans Jørgen.

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