[tdhf]¶
The [tdhf] section controls TDHF, TDDFT, spin-flip TDDFT, MRSF-TDDFT, and
UMRSF-TDDFT response calculations. Use [input] method=tdhf to activate these
workflows.
Background¶
MRSF-TDDFT is OpenQP's main multistate response method. It starts from an open-shell high-spin reference, builds spin-flip response spaces, and mixes the reference density information so target states are less affected by ordinary spin-flip spin contamination. In practice this makes the same response machinery useful for multiconfigurational ground-state surfaces, excited-state surfaces, conical-intersection work, gradients, NACME, SOC, and MRSF-EKT. See References for the original theory papers and recent overview articles.
Minimal MRSF-TDDFT Example¶
.oqp:
mrsf(nstate=5)/bhhlyp/6-31g*
energy
geom="h2o.xyz"
Python:
from oqp.openqp import OpenQP
job = OpenQP("mrsf_keywords")
job.molecule(geometry="water", charge=0)
job.theory.mrsf(functional="bhhlyp", basis="6-31g*", nstate=5)
Legacy .inp:
[input]
method=tdhf
[scf]
type=rohf
multiplicity=3
[tdhf]
type=mrsf
nstate=5
Keywords¶
type¶
| Field | Value |
|---|---|
| Type | string |
| Default | rpa |
| Values | rpa, tda, sf, mrsf, umrsf, mrsf_ekt_ip, mrsf_ekt_ea |
| Used by | response model selection |
Selects the response model. Use mrsf for production MRSF-TDDFT workflows.
sf selects ordinary spin-flip TDDFT, and umrsf selects the unrestricted
MRSF energy path. The legacy mrsf_ekt_ip and mrsf_ekt_ea values are
energy-only; the current EKT workflow should use [input] runtype=ekt,
[tdhf] type=mrsf, and the [ekt] section.
MRSF and SF workflows require an ROHF reference in the current code path. UMRSF-TDDFT requires a UHF reference.
nstate¶
| Field | Value |
|---|---|
| Type | integer |
| Default | 1 |
| Used by | number of response roots |
Number of excited states to compute. It must be at least as large as the highest state requested by gradients, optimizations, NACME, SOC, Hessians, or EKT.
nstate_s, nstate_t¶
| Field | Value |
|---|---|
| Type | integer |
| Defaults | 0, 0 |
| Used by | unequal singlet/triplet SOC spaces |
Optional numbers of singlet and triplet roots for SOC. Zero means to use
nstate for that common count. In a .oqp file, do not set these
internal selectors directly; write soc(ns=3,nt=5). Both counts must be
provided together, and that form must not be combined with route nstate.
target¶
| Field | Value |
|---|---|
| Type | integer |
| Default | 1 |
| Used by | target-state workflows |
Target response state for workflows that read a single TDHF/MRSF state.
multiplicity¶
| Field | Value |
|---|---|
| Type | integer |
| Default | 1 |
| Used by | response-state spin selection |
Requested response-state multiplicity. For MRSF-TDDFT, this is the target spin multiplicity after spin flip, not necessarily the same as the high-spin ROHF reference multiplicity. For SOC, do not set this as a single target multiplicity; the SOC workflow computes singlet and triplet response roots internally.
maxit¶
| Field | Value |
|---|---|
| Type | integer |
| Default | 50 |
| Used by | Davidson/response solver |
Maximum number of response-solver iterations.
conv¶
| Field | Value |
|---|---|
| Type | float |
| Default | 1.0e-6 |
| Used by | response convergence |
Convergence threshold for the response solver.
nvdav¶
| Field | Value |
|---|---|
| Type | integer |
| Default | 50 |
| Used by | Davidson subspace |
Maximum Davidson subspace dimension. The input checker warns when nvdav is
smaller than nstate.
maxit_zv¶
| Field | Value |
|---|---|
| Type | integer |
| Default | 50 |
| Used by | Z-vector solver |
Maximum number of Z-vector iterations for gradient/property workflows.
zvconv¶
| Field | Value |
|---|---|
| Type | float |
| Default | 1.0e-6 |
| Used by | Z-vector convergence |
Convergence threshold for Z-vector equations.
z_solver¶
| Field | Value |
|---|---|
| Type | integer |
| Default | 0 |
| Values | 0, 1, 2, 3 |
| Used by | Z-vector linear solver |
Selects the Z-vector solver. In the source comments, 0 is CG, 1 is legacy
GMRES, 2 is MINRES, and 3 is AUTO.
gmres_dim¶
| Field | Value |
|---|---|
| Type | integer |
| Default | 50 |
| Used by | GMRES Z-vector solver |
Subspace dimension for GMRES when that solver is selected.
tlf¶
| Field | Value |
|---|---|
| Type | integer |
| Default | 2 |
| Used by | response-model internals |
Response-model selector used by the native TDHF/MRSF implementation.
hfscale, cam_alpha, cam_beta, cam_mu¶
| Field | Value |
|---|---|
| Type | float |
| Defaults | -1.0, -1.0, -1.0, -1.0 |
| Used by | response functional parameter overrides |
Override exact-exchange and CAM/range-separated parameters for response calculations. Negative values mean use the selected functional defaults.
spc_coco, spc_ovov, spc_coov¶
| Field | Value |
|---|---|
| Type | float |
| Default | -1.0 |
| Used by | spin-purification correction parameters |
Advanced MRSF/SF response parameters. Leave negative unless following a specific validated protocol.
conf_threshold¶
| Field | Value |
|---|---|
| Type | float |
| Default | 5.0e-2 |
| Used by | configuration analysis/output |
Threshold for reporting or using response configurations.
ixcore¶
| Field | Value |
|---|---|
| Type | string |
| Default | -1 |
| Used by | core-level response workflows |
Core-orbital selector for core-level response calculations such as X-ray absorption workflows.
resp_cutoff¶
| Field | Value |
|---|---|
| Type | float |
| Default | auto (follows perf; 1e-8 baseline) |
| Used by | MRSF-TDDFT — response 2e-integral cutoff |
2e-integral cutoff for the MRSF response build. 1e-8 is exact to ≪ µeV;
looser values (e.g. 1e-6) trade a few µeV for speed. Never tighter than the
SCF integral cutoff. See Performance.
fp32¶
| Field | Value |
|---|---|
| Type | string |
| Default | auto (follows perf; no preset enables it) |
| Values | on, off, auto |
| Used by | MRSF-TDDFT — single-precision response digestion |
Single-precision MRSF response Fock digestion. Non-reproducible and can flip near-degenerate states; net-slower than FP64 on CPU. Opt-in only.
zv_warmstart¶
| Field | Value |
|---|---|
| Type | string |
| Default | auto (follows perf; on at perf ≥ 1) |
| Values | on, off, auto |
| Used by | MRSF-TDDFT gradients — z-vector (CPHF) warm-start |
Reuse the previous geometry step's z-vector as the CG/GMRES initial guess (exact; the solve still converges to the same tolerance). Most effective across many nearby geometries (optimization, MD).