MRSF TDDFT SOC - Open-Quantum-Platform/openqp GitHub Wiki

Spin-Orbit Coupling with MRSF-TDDFT

OpenQP supports MRSF-TDDFT spin-orbit coupling (SOC) calculations through runtype=soc. The SOC workflow performs the reference SCF calculation once, computes the singlet MRSF-TDDFT states, computes the triplet MRSF-TDDFT states, and then evaluates the SOC matrix elements.

The implementation supports both one-electron SOC and the mean-field two-electron SOC contribution. The [input] soc_2e keyword controls which terms are included:

  • soc_2e=0: one-electron SOC only.
  • soc_2e=1: one-electron SOC plus mean-field two-electron SOC. This is the default.

Requirements

SOC calculations currently require:

  • [input] method=tdhf
  • [input] runtype=soc
  • [tdhf] type=mrsf
  • [scf] type=rohf
  • [scf] multiplicity=3

The triplet ROHF reference is used to generate both singlet and triplet MRSF-TDDFT state manifolds before the SOC step.

Example Input

[input]
system=ch3br.xyz
charge=0
runtype=soc
basis=6-31g*
functional=bhhlyp
method=tdhf
soc_2e=1

[guess]
type=huckel

[scf]
type=rohf
multiplicity=3
maxit=50

[tdhf]
type=mrsf
nstate=3

For one-electron SOC only, use:

[input]
soc_2e=0

Output

The SOC run prints the scalar MRSF-TDDFT state information and SOC-coupled results. JSON output also includes SOC data so downstream tools can inspect the coupled-state energies, eigenvectors, and SOC matrix elements.

Notes

  • Choose a basis and functional appropriate for the SOC target system. Heavy-atom systems can require effective core potentials or basis sets chosen for relativistic effects.
  • The SOC calculation is a single-point property workflow; it is distinct from geometry optimization and nonadiabatic coupling runtype workflows.
  • Use openqp --run_tests with SOC examples when validating a build that includes SOC support.

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