This keyword specifies that only half of the Brillouin zone will be used for summation during the exact exchange potential calculation. The NLXC_EXCHANGE_REFLECT_KPTS is the latest form of this keyword, while the obsolete version, EXCHANGE_REFLECT_KPTS, is supported for backward compatibility.
This is possible only if time reversal symmetry is assumed (see NLXC_IMPOSE_TRS).
NLXC_EXCHANGE_REFLECT_KPTS : TRUE
CASTEP keyword glossary
CASTEP parameters keywords