HF and DFT

HF and DFT calculations use [input] method=hf. Set [input] functional only for DFT; leaving it empty gives Hartree-Fock.

Energy

Input style:

[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

Python style:

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())

Runnable input: examples/HF/H2O_RHF-HF_ENERGY.inp.

Gradient

For a DFT gradient, request runtype=grad, set a functional, and use [properties] grad=0 for the reference-state gradient. In Python, the same choice is written as job.workflow.gradient(state=0).

Input style:

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

[properties]
grad=0

Python style:

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()

Runnable input: examples/DFT/H2O_RHF-DFT_GRADIENT.inp.

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.