# XC

Parameters needed for the calculation of the eXchange and Correlation potential [Edit on GitHub]

Subsections

- ADIABATIC_RESCALING
- GCP_POTENTIAL
- HF
- HFX_KERNEL
- VDW_POTENTIAL
- WF_CORRELATION
- XC_FUNCTIONAL
- XC_GRID
- XC_KERNEL
- XC_POTENTIAL

## Keywords

- 2ND_DERIV_ANALYTICAL

- 3RD_DERIV_ANALYTICAL

- DENSITY_CUTOFF

- DENSITY_SMOOTH_CUTOFF_RANGE

- FUNCTIONAL_ROUTINE

- GRADIENT_CUTOFF

- NSTEPS

- STEP_SIZE

- TAU_CUTOFF

## Keyword descriptions

2ND_DERIV_ANALYTICAL: logical = T

  Lone keyword: `T`

  Usage: 2ND_DERIV_ANALYTICAL logical

  Use analytical formulas or finite differences for 2nd derivatives of XC [Edit on GitHub]

3RD_DERIV_ANALYTICAL: logical = T

  Lone keyword: `T`

  Usage: 3RD_DERIV_ANALYTICAL logical

  Use analytical formulas or finite differences for 3rd derivatives of XC [Edit on GitHub]

DENSITY_CUTOFF: real = 1.00000000E-010

  Usage: density_cutoff 1.e-11

  The cutoff on the density used by the xc calculation [Edit on GitHub]

DENSITY_SMOOTH_CUTOFF_RANGE: real = 0.00000000E+000

  Usage: DENSITY_SMOOTH_CUTOFF_RANGE {real}

  Parameter for the smoothing procedure in xc calculation [Edit on GitHub]

FUNCTIONAL_ROUTINE: enum = DEFAULT

  Usage: FUNCTIONAL_ROUTINE (DEFAULT|TEST_LSD|DEBUG)

  Valid values:

  - `DEFAULT` Carry out exchange-correlation functional calculation

  - `TEST_LSD` Use test local-spin-density approximation code for exchange-correlation functional calculation

  - `DEBUG` Use debug new code for exchange-correlation functional calculation

  Select the code for xc calculation [Edit on GitHub]

GRADIENT_CUTOFF: real = 1.00000000E-010

  Usage: gradient_cutoff 1.e-11

  The cutoff on the gradient of the density used by the xc calculation [Edit on GitHub]

NSTEPS: integer = 3

  Usage: NSTEPS 4

  Number of steps to consider in each direction for the numerical evaluation of XC derivatives. Must be a value from 1 to 4 (Default: 3). [Edit on GitHub]

STEP_SIZE: real = 1.00000000E-003

  Usage: STEP_SIZE 1.0E-3

  Step size in terms of the first order potential for the numerical evaluation of XC derivatives [Edit on GitHub]

TAU_CUTOFF: real = 1.00000000E-010

  Usage: tau_cutoff 1.e-11

  The cutoff on tau used by the xc calculation [Edit on GitHub]