Section Linear Response::Sternheimer
Whether initial linear-response wavefunctions should be orthogonalized or not against the occupied states, at the start of each SCF cycle. Default is true only if SmearingFunction = semiconducting, or if the Occupations block specifies all full or empty states, and we are not solving for linear response in the occupied subspace too.
sternheimer/sternheimer.F90 : 192
call parse_variable(namespace, 'Preorthogonalization', default_preorthog, this%preorthogonalization)