HF and DFT

HF and DFT use a basis-only or functional/basis .oqp route. The legacy keyword form uses [input] method=hf; setting [input] functional selects DFT, while leaving it empty gives Hartree-Fock.

Energy

.oqp:

hf/6-31g*
energy
geom="h2o.xyz"

energy is the default driver and may also be omitted.

Python:

from oqp.openqp import OpenQP

job = OpenQP("h2o_hf", silent=1)
job.molecule(geometry="water", charge=0, multiplicity=1)
job.theory.hf(basis="6-31g*")

mol = job.run()
print("SCF energy:", mol.get_scf_energy())

Legacy .inp:

[input]
system=
   O   0.000000000   0.000000000  -0.041061554
   H  -0.533194329   0.533194329  -0.614469223
   H   0.533194329  -0.533194329  -0.614469223
charge=0
runtype=energy
basis=6-31g*
method=hf

[guess]
type=huckel

[scf]
type=rhf
multiplicity=1

Runnable .oqp: examples/HF/H2O_RHF-HF_ENERGY.oqp. The same-stem .inp file is retained for legacy use.

Gradient

For a DFT ground-state gradient, grad and grad(S0) are equivalent. In Python, the same choice is written as job.workflow.gradient(state=0).

.oqp:

dft/bhhlyp/6-31g*
grad
geom="h2o.xyz"

Python:

from oqp.openqp import OpenQP

job = OpenQP("h2o_dft_grad", silent=1)
job.molecule(geometry="water", charge=0, multiplicity=1)
job.theory.dft(functional="bhhlyp", basis="6-31g*")
job.workflow.gradient(state=0)

mol = job.run()
gradient = mol.get_grad()

Legacy .inp:

[input]
runtype=grad
method=hf
functional=bhhlyp
basis=6-31g*

[properties]
grad=0

Runnable .oqp: examples/DFT/H2O_RHF-DFT_GRADIENT.oqp. The same-stem .inp file is retained for legacy use.

Hessian

HF/DFT Hessians are run with runtype=hess and controlled by [hess]. Analytical and numerical Hessian examples are collected on the Hessian and Frequencies workflow page.