Advanced Occupation Options

By default the levels are occupied according to the aufbau principle. In some cases it is possible to create holes below the Fermi level or uneven occupation for alpha and beta electrons with the Occupations (\(\Gamma\)-only) and alternatively the EnforcedSpinPolarization (for an arbitrary number of k-points) key.

Occupations # Non-standard block. See details.
   ...
End

Occupations

Type

Non-standard block

Description

Allows one to input specific occupations numbers. Applies only for calculations that use only one k-point (i.e. pseudo-molecule calculations). See example.

Example:

OCCUPATIONS
   1 occupations_alpha {// occupations_beta}
End

• occupations_beta and the separating double slash (//) must not be used in a spin-restricted calculation.

• occupations_alpha/beta is a sequence of values assigned to the states (‘bands’) in energy ordering.

ElectronHole
   BandIndex integer
   SpinIndex integer
End

ElectronHole

Type

Block

Description

Allows one to specify an occupied band which shall be depopulated, where the electrons are then moved to the Fermi level. For a spin-restricted calculation 2 electrons are shifted and for a spin-unrestricted calculation only one electron is shifted.

BandIndex

Type

Integer

Description

Which occupied band shall be depopulated.

SpinIndex

Type

Integer

Description

Defines the spin of the shifted electron (1 or 2).

See the example Si_ElectronHole

Finally, also the Convergence%StartWithMaxSpin influences (indirectly) the final state. Running for instance the H2 molecule with a PBE functional preserves the triplet state through the SCF (not being the ground state).