Examples

The OpenQP example inputs are the preferred source of runnable input decks. Use them as templates before writing a new input from scratch.

For self-contained inputs with reference results and explanations, start with the Worked Examples.

Use the canonical .oqp examples. Shared Cartesian coordinates live in examples/geometries.

Folder	Contents
examples/HF	RHF, ROHF, and UHF Hartree-Fock energies and gradients.
examples/DFT	DFT energies, gradients, and optimization examples.
examples/MP2	Standalone MP2 energy and analytic RHF-gradient reference examples.
examples/SCF	SCF convergence controls such as DIIS variants, MOM, pFON, and SOSCF.
examples/TDHF	TDHF energy and gradient examples.
examples/TDDFT	TDDFT energy and gradient examples.
examples/SF-TDDFT	Spin-flip TDDFT examples.
examples/MRSF-TDDFT	MRSF-TDDFT energies, gradients, and optimization data.
examples/OPT	Native optimization including frozen-distance constraints, MECI including the BaekA multistate regression, MECP, TS, IRC, NEB, and MEP; the TCI-named deck is retained for compatibility.
examples/HESS	Analytic and numerical Hessian workflows.
examples/PCM	ddX reference-SCF PCM energy cases.
examples/SOC	MRSF-TDDFT SOC cases.
examples/NMR	NMR shielding examples.
examples/TRAH	TRAH SCF examples.
examples/ISPHER	Spherical-harmonic AO convention examples.
examples/ECP	Effective-core-potential examples.
examples/UMRSF-TDDFT	UMRSF-TDDFT energy and analytic-gradient examples (Cartesian and spherical-harmonic bases).
examples/XAS	X-ray absorption examples.
examples/MD	Gas-phase ground-state Born--Oppenheimer MD with md(...).
examples/ODP	ODP umbrella windows for MRSF-TDDFT NAMD: an NVE window, the same window in Langevin NVT, a checkpoint-continuation script (odp_restart.py) and the WHAM analysis script (odp_wham.py); see ODP Umbrella Sampling.
examples/QMMM	ESPF electrostatic QM/MM (requires OpenMM): NAMD / SOC-NAMD dynamics, ground-state QM/MM MD with checkpoints and phase-space snapshots, QM/MM optimization, covalent-boundary (link atom + frontier_scheme), and single-point energies.

Run a single example:

openqp examples/HF/H2O_RHF-HF_ENERGY.oqp

For the standalone MP2 example:

openqp examples/MP2/h2o_ump2_6-31g.oqp

For the analytic RHF-MP2 gradient example:

openqp examples/MP2/h2o_rmp2_6-31g_grad.oqp

Run the packaged example tests:

openqp --run_tests all --input-format oqp      # standard suite through .oqp

Use --input-format oqp for canonical-file regression. The standard suite retains its slow/non-self-contained exclusions; each calculation gets an isolated output folder.

Geometry and reaction-path examples use the native OpenQP engine, including HCN_RHF-DFT_CONSTRAINED_OQP.oqp, which demonstrates a frozen C-N distance. The optional geomeTRIC adapter is retained for external compatibility but is not required by the standard example suite.

QM/MM examples

The examples/QMMM decks exercise ESPF electrostatic QM/MM (a QM region embedded in an OpenMM MM environment). They require the optional OpenMM backend (pip install openmm) and read their *.pdb / *.xml auxiliary files from the same folder. The nonadiabatic (runtype=namd) decks are part of openqp --run_tests all and are reported SKIPPED without OpenMM; the ground-state (runtype=md) and single-point decks are skipped by the suite — run them directly.

Deck	Type	What it shows
H2CO-water_BHHLYP-MRSF-NAMD-QMMM.oqp	NAMD	MRSF-TDDFT Tully FSSH (internal conversion, md(soc=false)) with ESPF QM/MM: formaldehyde QM + 5 TIP3P waters, NoCutoff cluster.
H2CO-water_BHHLYP-SOC-NAMD-QMMM.oqp	SOC-NAMD	Intersystem crossing on the spin-adiabatic manifold with ESPF QM/MM, using the same system.
H2CO-water_BHHLYP-MRSF-NAMD-QMMM-SCHEME.oqp	NAMD	The unified form: namd(...) names the state and the complete scheme, md(...) the nuclear controls, qmmm(...) the embedding.
H2CO-water_BHHLYP-MRSF-NAMD-QMMM-NAC.oqp	NAMD	QM/MM surface hopping with analytic MRSF NAC (scheme=NAC).
H2CO-water_BHHLYP-MRSF-NAMD-QMMM.restart.oqp	NAMD restart	Continues H2CO-water_BHHLYP-MRSF-NAMD-QMMM.oqp from its checkpoint; run the producer first.
H2CO-water_RKS-QMMM-MD-SNAPSHOTS.oqp	Ground-state MD	NVT QM/MM equilibration that writes a checkpoint and numbered phase-space snapshots.
H2CO-water_BHHLYP-MRSF-NAMD-QMMM-SNAPSHOT.oqp	NAMD	QM/MM surface hopping started with md(snapshot=...) from an equilibrated snapshot.
ala-dipeptide_BHHLYP-MRSF-NAMD-QMMM-linkatom.oqp	NAMD	QM/MM surface hopping across a covalent boundary with a scheme that does not use analytic NAC.
ala-dipeptide_RKS-QMMM-GROUND-STATE-MD.oqp	Ground-state MD	Ground-state QM/MM MD in the unified md(...) qmmm(...) form.
ala-dipeptide_RHF-QMMM-OPT-linkatom.oqp	Optimization	QM/MM geometry optimization across a covalent boundary.
ala-box_BHHLYP-MRSF-NAMD-QMMM-PME.oqp	NAMD	The same covalent boundary in a periodic TIP3P box (cutoff=PME, Ewald QM/MM electrostatics), exercising ewald_tol, lj_switch, h_lj and mm_charge_width.
ala-box_BHHLYP-MRSF-NAMD-QMMM-PME-FLEXIBLE-ODP.oqp	NAMD (NVT, ODP)	The periodic box with one water moved into the QM region and kept near the solute by the FlexiBLE boundary, sampled as one ODP umbrella window in Langevin NVT.
ala-dipeptide_BHHLYP-QMMM-MD-RCD.oqp	Ground-state MD	QM/MM MD across a covalent boundary: alanine dipeptide, QM = the C-terminal amide, hydrogen link-atom cap + frontier_scheme=rcd.
run.oqp	Ground-state MD	Whole-molecule QM region: one water of a water dimer.
ala.oqp	Single-point	QM/MM energy of the alanine amide.
2E4E_RHF-DFT-QMMM_energy.oqp	Single-point	QM/MM energy on a protein fragment.

Run a NAMD-QMMM example:

openqp examples/QMMM/H2CO-water_BHHLYP-MRSF-NAMD-QMMM.oqp

Run the covalent-boundary ground-state QM/MM MD example (from the folder, so the PDB/force-field files resolve):

cd examples/QMMM && openqp ala-dipeptide_BHHLYP-QMMM-MD-RCD.oqp

Repository maintainers can regenerate and audit the concise companions after editing legacy examples with python tools/convert_legacy_examples.py --write. Running the command without --write performs a dry-run audit. The converter refuses a file when an explicitly written legacy setting cannot be represented faithfully; it does not silently create a reduced calculation.

See the qmmm keyword page for the input contract and covalent QM/MM boundaries, and the SOC-NAMD-QMMM workflow for the nonadiabatic path.

When adding a new manual page, link to an OpenQP repository example whenever possible instead of pasting a long input deck into prose.