4.7. FOD and FLO generation

This example is about the generation of Fermi orbital descriptors (FODs).

Afterward, Fermi-Löwdin orbitals (FLOs) can be generated as well.

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from eminus import Atoms, read, SCF
from eminus.dft import get_psi
from eminus.extras import get_fods, remove_core_fods
from eminus.localizer import get_FLO

Start by with a DFT calculation for methane

atom, pos = read("CH4.xyz")
atoms = Atoms(atom, pos, ecut=10, center=True)
scf = SCF(atoms)
scf.run()

Calculate all FODs

fods_all = get_fods(atoms)
print(f"\nAll FODs:\n{fods_all}")

Remove core FODs, since the calculation uses a GTH pseudopotential

fods = remove_core_fods(atoms, fods_all)
print(f"\nCore FODs:\n{fods}")

The quality from the FOD guess can vary, but you can use these as a decent guess

# import numpy as np
# fods = [np.array([[10.71617803, 10.75510917, 10.73689087],
#                   [10.82635834,  9.25127336,  9.25068483],
#                   [ 9.24857483, 10.79169744,  9.24052496],
#                   [ 9.25441172,  9.25005662, 10.82402898]]),
#         np.array([])]

Write the FODs to an XYZ file to view them

atoms.write("CH4_fods.xyz", fods)

Generate the Kohn-Sham orbitals

psi = get_psi(scf, scf.W)

Calculate the FLOs

FLO = get_FLO(atoms, psi, fods)

Write all FLOs to CUBE files

print("\nWrite cube files:")
for i in range(atoms.occ.Nstate):
    print(f"{i + 1} of {atoms.occ.Nstate}")
    atoms.write(f"CH4_FLO_{i + 1}.cube", FLO[0][0, :, i])

All of the functionality above can be achieved with the following workflow function

# from eminus.orbitals import FLO
# FLO = FLO(scf, write_cubes=True)

Download 07_fod_extra.py CH4.xyz