Quickstart

This quickstart runs a small MRSF-TDDFT calculation on water. You can start from either a standard OpenQP input file or the compact Python API.

Input File

Create h2o_mrsf.inp:

[input]
system=
   8   0.000000000   0.000000000  -0.041061554
   1  -0.533194329   0.533194329  -0.614469223
   1   0.533194329  -0.533194329  -0.614469223
charge=0
runtype=energy
basis=6-31g*
functional=bhhlyp
method=tdhf

[guess]
type=huckel

[scf]
type=rohf
multiplicity=3

[tdhf]
type=mrsf
nstate=3

Run it:

openqp h2o_mrsf.inp

Python Script

The same calculation can be set up from Python:

from oqp.openqp import OpenQP

job = OpenQP("h2o_mrsf", silent=1)
job.molecule(geometry="water", charge=0)
job.theory.mrsf(functional="bhhlyp", basis="6-31g*", nstate=3)

mol = job.run()
results = mol.get_results()

print("Ground/reference energy:", results["energy"])
print("TD energies:", results["td_energies"])

For MRSF-TDDFT, the Python theory helper supplies the required ROHF triplet reference internally. HF and DFT scripts can set multiplicity directly in job.molecule(...) when the molecular reference multiplicity is part of the ordinary SCF setup.

OpenQP writes a log and structured output files in the working directory. For more Python examples, see Run OpenQP from Python.

Next Calculations

Use these input files as nearby templates:

Goal	Example input
MRSF-TDDFT energy	examples/MRSF-TDDFT/H2O_BHHLYP-MRSFTDDFT_ENERGY.inp
RHF energy	examples/HF/H2O_RHF-HF_ENERGY.inp
DFT gradient	examples/DFT/H2O_RHF-DFT_GRADIENT.inp
Analytic HF/DFT Hessian	examples/HESS/H2O_RHF-DFT_ANA_HESS.inp
Native geometry optimization	examples/OPT/H2O_RHF-DFT_OPTIMIZE_OQP.inp
SOC	examples/SOC/H2O_BHHLYP_SOC.inp
PCM/ddX energy	examples/PCM/H2O_RHF-HF_DDPCM_ENERGY_ISPHER.inp
NMR shielding	examples/NMR/H2O_RHF-NMR.inp