Examples

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

Every sectioned *.inp deck has a same-stem readable *.oqp companion. The two files describe the same calculation, so new users can start from the shorter .oqp form while existing scripts can keep using .inp unchanged. Shared Cartesian coordinates used by the concise decks 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 reference-value 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 examples.
examples/XAS	X-ray absorption examples.
examples/QMMM	ESPF electrostatic QM/MM (requires OpenMM): NAMD / SOC-NAMD dynamics, ground-state QM/MM MD, 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

Run the packaged example tests:

openqp --run_tests all                         # automatic mixed regression set
openqp --run_tests all --input-format inp      # standard suite through .inp
openqp --run_tests all --input-format oqp      # standard suite through .oqp
openqp --run_tests all --input-format both     # both syntaxes in that suite

The default auto mode prefers .oqp, retains any .inp without a concise companion, and keeps a small representative .inp compatibility set. The historical all scope still excludes unusually slow or non-self-contained examples. Supplying an explicit directory instead applies the selected format to every matching input below that directory. Each calculation receives an isolated output folder, so paired .inp/.oqp logs and fixed-name optimization artifacts cannot overwrite one another.

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.
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.