# PERIODIC_CORRECTION

Parameters influencing correction for periodic GW. Old method, not recommended to use [Edit on GitHub]

## Keywords

- AVERAGE_DEGENERATE_LEVELS

- DO_AUX_BAS_GW

- EPS_EIGENVAL

- EPS_KPOINT

- EXTRAPOLATE_KPOINTS

- FRACTION_AUX_MOS

- KPOINTS

- MO_COEFF_GAMMA

- NUM_KP_GRIDS

- NUM_OMEGA_POINTS

## Keyword descriptions

AVERAGE_DEGENERATE_LEVELS: logical = T

  Aliases: ADL

  Lone keyword: `T`

  Usage: AVERAGE_DEGENERATE_LEVELS

  If true, the correlation self-energy of degenerate levels is averaged. [Edit on GitHub]

DO_AUX_BAS_GW: logical = F

  Lone keyword: `T`

  Usage: DO_AUX_BAS_GW TRUE

  If true, use a different basis for the periodic correction. This can be necessary in case a diffused basis is used for GW to converge the HOMO-LUMO gap. In this case, numerical problems may occur due to diffuse functions in the basis. This keyword only works if AUX_GW <basis set> is specified in the kind section for every atom kind. [Edit on GitHub]

EPS_EIGENVAL: real = 2.00000000E-004

  Usage: EPS_EIGENVAL 1.0E-5

  Threshold for considering levels as degenerate. Unit: Hartree. [Edit on GitHub]

EPS_KPOINT: real = 1.00000000E-005

  Usage: EPS_KPOINT 1.0E-4

  If the absolute value of a k-point is below EPS_KPOINT, this kpoint is neglected since the Gamma point is not included in the periodic correction. [Edit on GitHub]

EXTRAPOLATE_KPOINTS: logical = T

  Aliases: EXTRAPOLATE

  Lone keyword: `T`

  Usage: EXTRAPOLATE_KPOINTS FALSE

  If true, extrapolates the k-point mesh. Only working if k-point mesh numbers are divisible by 4, e.g. 8x8x8 or 12x12x12 is recommended. [Edit on GitHub]

FRACTION_AUX_MOS: real = 5.00000000E-001

  Usage: FRACTION_AUX_MOS 0.6

  Fraction how many MOs are used in the auxiliary basis. [Edit on GitHub]

KPOINTS: integer[3] = 16 16 16

  Keyword can be repeated.

  Usage: KPOINTS nx ny nz

  Specify number of k-points for a single k-point grid. Internally, a Monkhorst-Pack grid is used. Typically, even numbers are chosen such that the Gamma point is excluded from the k-point mesh. [Edit on GitHub]

MO_COEFF_GAMMA: logical = T

  Lone keyword: `T`

  Usage: MO_COEFF_GAMMA

  If true, only the MO coefficients at the Gamma point are used for the periodic correction. Otherwise, the MO coeffs are computed at every k-point which is much more expensive. It should be okay to use the Gamma MO coefficients. [Edit on GitHub]

NUM_KP_GRIDS: integer = 1

  Usage: NUM_KP_GRIDS 5

  Number of k-point grids around the Gamma point with different resolution. E.g. for KPOINTS 4 4 4 and NUM_KP_GRIDS 3, there will be a 3x3x3 Monkhorst-Pack (MP) k-point grid for the whole Brillouin zone (excluding Gamma), another 3x3x3 MP grid with smaller spacing around Gamma (again excluding Gamma) and a very fine 4x4x4 MP grid around Gamma. [Edit on GitHub]

NUM_OMEGA_POINTS: integer = 300

  Usage: NUM_OMEGA_POINTS 200

  Number of Clenshaw-Curtis integration points for the periodic correction in cubic- scaling GW. This variable is a dummy variable for canonical N^4 GW calculations. [Edit on GitHub]