#
NLXC_IMPOSE_TRS or IMPOSE_TRS (.param)

## Keyword type

Logical

## Description

This keyword imposes time reversal symmetry on the gamma point wavefunctions. Time reversal symmetry is a necessary property of any
Kohn-Sham orbital. NLXC_EXCHANGE_REFLECT_KPTS is the latest form of this keyword, while the obsolete version, EXCHANGE_REFLECT_KPTS, is
supported for backward compatibility.

In the reciprocal space representation, time reversal symmetry means that the coefficient of plane wave |k + g> must be the conjugate of
the coefficient of plane wave |-k - g>. With the standard LDA and GGA exchange-correlation functionals, the absence of such symmetry does
not affect the total energies or densities and can therefore be ignored. However, when using exact or screened exchange, the total energy may
be incorrect if time reversal symmetry is not present. Also, the efficiency of calculation of the exchange operator is significantly improved
by assuming time reversal symmetry (see also NLXC_EXCHANGE_REFLECT_KPTS.

## Default

FALSE

## Example

NLXC_IMPOSE_TRS : TRUE

###### See Also:

NLXC_EXCHANGE_REFLECT_KPTS

CASTEP keyword glossary

CASTEP parameters keywords

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