# XC_KERNEL

The xc kernel to use (CAREFUL: xc kernel here refers to kernels that are not derived from an xc functional, but rather are modelled directly. This kernel will be used in a TDDFPT calculation. Cannot be combined with XC_FUNCTIONAL or XC_POTENTIAL. [Edit on GitHub]

## Keywords

- SECTION_PARAMETERS

- C_CAA

- C_CAB

- C_XAA

- GAMMA

- PARAMETER

- SCALE_C

- SCALE_X

## Keyword descriptions

SECTION_PARAMETERS: enum = NONE

  Lone keyword: `NONE`

  Usage: &XC_KERNEL LDAfxc

  Valid values:

  - `PADEFXC` Fxc based on LDA PADE approximation

  - `LDAFXC` Fxc based on LDA functionals

  - `GGAFXC` Fxc model from fit to PBE functional

  - `NONE` NONE

  Selection of kernel functionals. [Edit on GitHub]

C_CAA: real[3] = 1.70000000E-001 2.35000000E+000 -2.55000000E+000

  Usage: C_CAA <REAL> <REAL> <REAL>

  B97 C parameters for opposite spin correlation. [Edit on GitHub]

C_CAB: real[3] = 1.00000000E+000 7.50000000E-001 -4.60000000E+000

  Usage: C_CAB <REAL> <REAL> <REAL>

  B97 C parameters for same spin correlation. [Edit on GitHub]

C_XAA: real[3] = 1.00000000E+000 6.30000000E-001 9.40000000E-001

  Usage: C_XAA <REAL> <REAL> <REAL>

  B97 C parameters for exchange [Edit on GitHub]

GAMMA: real[3] = 4.00000000E-003 6.00000000E-003 2.00000000E-001

  Usage: GAMMA <REAL> <REAL> <REAL>

  B97 GAMMA parameters [gx, gab, gaa] [Edit on GitHub]

PARAMETER: real[ ]

  Usage: PARAMETER <REAL> .. <REAL>

  List of parameters specific to the kernel function [Edit on GitHub]

SCALE_C: real = 1.00000000E+000

  Usage: SCALE_C 0.2

  Scaling parameter for correlation kernel. [Edit on GitHub]

SCALE_X: real = 1.00000000E+000

  Usage: SCALE_X 0.2

  Scaling parameter for exchange kernel. [Edit on GitHub]