Syntax:

exchange-regularization <method>=AuxiliaryFunction|None|ProbeChargeEwald|SphericalTruncated|WignerSeitzTruncated

Description:

Regularization / singularity correction method for exact exchange. The allowed methods and defaults depend on the setting of <geometry> in command coulomb-interaction

None

No singularity correction: default and only option for non-periodic systems with no G=0 singularity (<geometry> = Spherical / Isolated). This is allowed for fully or partially periodic systems, but is not recommended due to extremely poor convergence with number of k-points.
AuxiliaryFunction

G=0 modification based on numerical integrals of an auxiliary function, as described in Ref. [4] Allowed for 3D/2D/1D periodic systems.
ProbeChargeEwald

G=0 modification based on the Ewald sum of a single point charge per k-point sampled supercell. Valid for 3D/2D/1D periodic systems.
SphericalTruncated

Truncate exchange kernel on a sphere whose volume equals the k-point sampled supercell, as in Ref. [26]. Allowed for any (partially) periodic <geometry>, but is recommended only when the k-point sampled supercell is roughly isotropic.
WignerSeitzTruncated

Truncate exchange kernel on the Wigner-Seitz cell of the k-point sampled supercell, as in Ref. [27]. Default for any (partially) periodic <geometry>.

Properties:

Requires: coulomb-interaction

Forbids: (None)

Allow multiple: no

Default:

exchange-regularization WignerSeitzTruncated

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