DFT Calculations

OpenQuantum runs Kohn–Sham DFT through either Gaussian-style route cards or the section-based input format. These examples cover the available functional rungs, grid control, open-shell DFT, and dispersion-corrected functionals.

Closed-shell GGA (PBE)

title: Water PBE single point

MOLECULE
  Charge 0
  Multiplicity 1
  Units Angstrom
END

task: pbe sto-3

SCF
  MaxCycle 50
  Conver 8
END

INT
  Grid UltraFine
END

GEOMETRY
O 0.000000  0.000000  0.117000
H 0.000000  0.755000 -0.471000
H 0.000000 -0.755000 -0.471000
END

The output reports the functional rung, grid level, the integrated XC energy, the grid electron count, and the signed grid integration error.

Hybrid GGA (B3LYP, PBE0)

title: Water B3LYP

MOLECULE
  Charge 0
  Multiplicity 1
  Units Angstrom
END

task: b3lyp sto-3g

SCF
  MaxCycle 50
  Conver 8
END

INT
  Grid UltraFine
END

GEOMETRY
O 0.000000  0.000000  0.117000
H 0.000000  0.755000 -0.471000
H 0.000000 -0.755000 -0.471000
END

Hybrid functionals mix exact exchange (20% for B3LYP, 25% for PBE0) into the Fock build, so they require electron-repulsion integrals in addition to the grid quadrature.

Meta-GGA (TPSS, M06-L)

title: H2 M06-L

MOLECULE
  Charge 0
  Multiplicity 1
  Units Angstrom
END

task: m06l sto-3g 

SCF
  MaxCycle 50
  Conver 8
END

INT
  Grid UltraFine
END

GEOMETRY
H 0.0 0.0 0.0
H 0.0 0.0 0.74
END

M06-L correlation uses the full VS98 working factor with the reduced-gradient polynomial baseline, so opposite-spin correlation integrates physically on the standard grid. Meta-GGAs use kinetic-energy density and benefit from a finer grid; int=superfine is recommended for production runs.

Hybrid meta-GGA (M06-2X)

title: H2 M06-2X 

MOLECULE
  Charge 0
  Multiplicity 1
  Units Angstrom
END

task: m062x sto-3g 

SCF
  MaxCycle 50
  Conver 8
END

INT
  Grid UltraFine
END

GEOMETRY
H 0.0 0.0 0.0
H 0.0 0.0 0.74
END

M06-2X adds 54% exact exchange on top of the meta-GGA semilocal terms.

Range-separated hybrid with dispersion (ωB97X-D)

title: Water omegaB97X-D

MOLECULE
  Charge 0
  Multiplicity 1
  Units Angstrom
END

task: wb97xd sto-3g 

SCF
  MaxCycle 50
  Conver 8
END

INT
  Grid UltraFine 
END

GEOMETRY
O 0.000000  0.000000  0.117000
H 0.000000  0.755000 -0.471000
H 0.000000 -0.755000 -0.471000
END

ωB97X-D splits the Coulomb operator into short- and long-range exchange and adds an empirical D2 dispersion correction to the total energy. The job header lists the range-separation parameter ω and the dispersion tag.

Open-shell DFT (UKS)

title: H atom PBE doublet

MOLECULE
  Charge 0
  Multiplicity 2
  Units Angstrom
END

task: PBE STO-3G

SCF
  MaxCycle 50
  Conver 8
END

GEOMETRY
H 0.0 0.0 0.0
END

Any non-singlet multiplicity dispatches an unrestricted Kohn–Sham calculation with spin-resolved XC potentials.

Section-format DFT with explicit grid

title: Water PBE0 section input

MOLECULE
  Charge 0
  Multiplicity 1
  Units Angstrom
END

task: STO-3G

DFT
  Functional PBE0
  Grid UltraFine
END

SCF
  MaxCycle 100
  Conver 8
END

GEOMETRY
O 0.000000  0.000000  0.117000
H 0.000000  0.755000 -0.471000
H 0.000000 -0.755000 -0.471000
END

Custom angular grid

A six-digit grid code requests an explicit radial × angular grid. Angular orders up to 302 use genuine Lebedev–Laikov grids:

#p m06l/sto-3g int=grid=099302

H2 with 99 x 302 grid

0 1
H 0.0 0.0 0.0
H 0.0 0.0 0.74

Choosing a grid

  • Coarse / Medium — quick smoke tests and early development.
  • Fine / UltraFine — typical GGA and hybrid production runs.
  • SuperFine or a custom 099302 grid — meta-GGA and M06-family functionals, which are most sensitive to angular and radial resolution.