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quack/src/eDFT/RMFL20_lda_exchange_energy.f90

47 lines
1002 B
Fortran

subroutine RMFL20_lda_exchange_energy(nEns,wEns,nGrid,weight,rho,Ex)
! Compute the restricted version of the Marut-Fromager-Loos weight-dependent exchange functional
! The RMFL20 is a two-state, single-weight exchange functional
implicit none
include 'parameters.h'
! Input variables
integer,intent(in) :: nEns
double precision,intent(in) :: wEns(nEns)
integer,intent(in) :: nGrid
double precision,intent(in) :: weight(nGrid)
double precision,intent(in) :: rho(nGrid)
! Local variables
integer :: iG
double precision :: Cxw
double precision :: r
! Output variables
double precision :: Ex
! Weight-denepdent Cx coefficient
Cxw = CxLDA + wEns(2)*(Cx1 - Cx0)
! Compute LDA exchange energy
Ex = 0d0
do iG=1,nGrid
r = max(0d0,rho(iG))
if(r > threshold) then
Ex = Ex + weight(iG)*Cxw*r**(4d0/3d0)
endif
enddo
end subroutine RMFL20_lda_exchange_energy