# EXACT_EXCHANGE

Whether exact-exchange should be added to the kernel and if so, with which fraction and operator. [Edit on GitHub]

Subsections

- RI_METRIC

## Keywords

- SECTION_PARAMETERS

- CUTOFF_RADIUS

- EPS_RANGE

- EPS_SCREENING

- OMEGA

- POTENTIAL_TYPE

- SCALE

- T_C_G_DATA

## Keyword descriptions

SECTION_PARAMETERS: logical = F

  Lone keyword: `T`

  Usage: &EXACT_EXCHANGE {logical}

  Enables the addition of exact exchange to the kernel. [Edit on GitHub]

CUTOFF_RADIUS: real = 0.00000000E+000

  Aliases: R_C ,RC ,RANGE

  Usage: CUTOFF_RADIUS {double}

  The cutoff radius (in Angstrom) for the truncated Coulomb operator. [Edit on GitHub]

EPS_RANGE: real = 1.00000000E-006

  Usage: EPS_RANGE = {double}

  The threshold to determine the effective range of the short range operator: erfc(omega*eff_range)/eff_range = EPS_RANGE [Edit on GitHub]

EPS_SCREENING: real = 1.00000000E-008

  Aliases: EPS_SCREEN

  A threshold to determine which primitive 3-center integrals are kept for contraction, as the latter operation can be expensive (especially for large basis sets ). If |(ab|c)| < EPS_SCREENNING, it is discarded. [Edit on GitHub]

OMEGA: real = 0.00000000E+000

  Usage: OMEGA {double}

  The range parameter for the short range operator (in 1/a0). [Edit on GitHub]

POTENTIAL_TYPE: enum = COULOMB

  Aliases: OP ,OPERATOR ,POTENTIAL

  Usage: OPERATOR {string}

  Valid values:

  - `COULOMB` Standard Coulomb operator: 1/r

  - `TRUNCATED` Truncated Coulomb operator: 1/r if r < R_c, 0 otherwise

  - `SHORTRANGE` Short range: erfc(omega*r)/r

  The type of operator used for exact exchange. The standard Coulomb operator cannot be used in periodic systems. [Edit on GitHub]

SCALE: real = 1.00000000E+000

  Aliases: FRACTION

  Scaling of the exact exchange contribution. [Edit on GitHub]

T_C_G_DATA: string = t_c_g.dat

  Usage: T_C_G_DATA {string}

  Location of the file t_c_g.dat that contains the data for the evaluation of the truncated gamma function [Edit on GitHub]