Canonical .oqp input files

Use .oqp for every new input, tutorial and linked example. This URL is kept so existing links now lead to the canonical format. Start with the complete syntax or the keyword reference.

Minimal input

mrsf(nstate=3)/bhhlyp/6-31g* opt(S0)
geom="h2o.xyz"

Save this as h2o_mrsf.oqp and run openqp h2o_mrsf.oqp. The route selects method/functional/basis and opt(S0) selects the physical ground-state optimization. OpenQP supplies the MRSF high-spin reference internally.

Geometry

Use geom="h2o.xyz" or an inline triple-quoted atom table:

hf/6-31g*
geom="""
O 0.000000000 0.000000000 -0.041061554
H -0.533194329 0.533194329 -0.614469223
H 0.533194329 0.533194329 -0.614469223
"""

Coordinates are in angstrom. Use geom2="other.xyz" when the selected calculation requires a second geometry. Relative paths resolve from the input file's directory. See geometry and globals.

Core controls

Purpose	Canonical form
Theory and basis	hf/6-31g*, dft/pbe0/def2-svp, mrsf(nstate=3)/bhhlyp/6-31g*
Molecule and workers	geom="molecule.xyz" charge=0 omp_threads=8
SCF	scf(conv=1e-8,maxit=100)
Initial orbitals	guess(type=huckel)
DFT grid	dftgrid(pruned=SG2)
Gradient or optimization	grad(S1) or opt(S1,maxit=100) in separate files
Dynamics	namd(S1,scheme=Overlap) md(nstep=10,dt=0.5)
Environment	pcm(...) or qmmm(...) with their required assets

These forms are signatures or alternatives, not one combined runnable input. The detailed controls describe defaults, units and restrictions. A raw internal field without a canonical spelling is not an available .oqp input option.

State selection

MRSF physical S0 maps to internal response root 1 and S1 to root 2; ordinary TDDFT S0 is the SCF reference. SF uses root=N because spin character is diagnosed after calculation. Write physical labels in the primary calculation and do not copy internal state indices into the route. See state and driver rules.

Optimizers and dynamics

Canonical geometry calculations use the native OpenQP optimizer. Put controls inside opt(...), ts(...), meci(...), mecp(...) or the applicable path calculation; do not write a second optimize(...) or oqp(...) call. Optional geomeTRIC/SciPy compatibility controls are API-only and cannot be made available by renaming an input file.

Nuclear controls belong in md(...); state selection and surface-hopping scheme belong in namd(...). QM/MM assets and partition belong in qmmm(...). For the supported OpenMM QM/MM workflows use openqp job.oqp --nompi. Follow dynamics and QM/MM for accepted combinations.

Validation

One primary calculation is permitted per file. Unknown keywords, conflicting aliases and incompatible states must fail validation. A parsed input does not establish numerical convergence or scientific support. Retain the exact canonical input and engine identity with the result; see migration and verification.