HF and DFT

Source access and public downloads

Repository paths identify files in the licensed engine source; they are not public downloads. For freely downloadable .oqp inputs and results, see Worked Examples.

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*
geom="h2o.xyz"

A single-point energy is the default task, so no energy keyword is needed; hf/6-31g* energy means the same thing.

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())

Canonical .oqp input:

rhf/6-31g*
geom="""
O   0.000000000   0.000000000  -0.041061554
H  -0.533194329   0.533194329  -0.614469223
H   0.533194329  -0.533194329  -0.614469223
"""

Runnable .oqp: examples/HF/H2O_RHF-HF_ENERGY.oqp.

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()

Canonical .oqp input:

rks/bhhlyp/6-31g* grad
geom="molecule.xyz"

Runnable .oqp: examples/DFT/H2O_RHF-DFT_GRADIENT.oqp.

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.

Scientific references

HF and density functional theory; Exchange-correlation functionals; Basis sets and effective core potentials.