#
NLXC_K_SCRN_AVERAGING_SCHEME or K_SCRN_AVERAGING_SCHEME (.param)

## Keyword type

String

## Description

This keyword determines the averaging scheme which is used for estimating the Thomas-Fermi screening length. The screening length
is an important parameter for calculating the screened nonlocal exchange. Available options are:

- AVE_DEN - Use averaged charge density. This option may be reasonable for 3D solids but not for systems
containing large regions of vacuum.
- SWA_DEN - Evaluate the self-weighted average charge density of the system and use the screening length
associated with this value. The self-weighted average is given by the integral of the density squared divided by the integral of the
density. This removes the problems connected with large regions of vacuum.
- SWA_ESX - Similar to SWA_DEN but instead the self-weighted average of
the screened-exchange energy density is estimated.

NLXC_K_SCRN_AVERAGING_SCHEME is the latest form of this keyword, while the obsolete version, K_SCRN_AVERAGING_SCHEME, is supported for
backward compatibility.

This keyword is relevant only for sX and
sX-LDA exchange correlation functionals.

## Default

AVE_DEN

## Example

NLXC_K_SCRN_AVERAGING_SCHEME : SWA_DEN

###### See Also:

CASTEP keyword glossary

CASTEP parameters keywords

Accelrys Materials Studio 8.0 Help: Wednesday, December 17, 2014