mirror of
https://github.com/pfloos/quack
synced 2024-10-31 19:23:52 +01:00
53 lines
1.1 KiB
Fortran
53 lines
1.1 KiB
Fortran
subroutine RGIC_lda_exchange_energy(nEns,wEns,nGrid,weight,rho,Ex)
|
|
|
|
! Compute the restricted version of the GIC 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 :: r
|
|
|
|
double precision :: a,b,c,w
|
|
double precision :: CxGIC
|
|
|
|
! Output variables
|
|
|
|
double precision :: Ex
|
|
|
|
! Weight-denepdent Cx coefficient
|
|
|
|
a = + 0.5751782560799208d0
|
|
b = - 0.021108186591137282d0
|
|
c = - 0.36718902716347124d0
|
|
|
|
w = wEns(2)
|
|
CxGIC = CxLDA*w*(1d0 - w)*(a + b*(w - 0.5d0) + c*(w - 0.5d0)**2)
|
|
|
|
! Compute GIC-LDA exchange energy
|
|
|
|
Ex = 0d0
|
|
|
|
do iG=1,nGrid
|
|
|
|
r = max(0d0,rho(iG))
|
|
|
|
if(r > threshold) then
|
|
Ex = Ex + weight(iG)*CxLDA*r**(4d0/3d0)
|
|
Ex = Ex + weight(iG)*CxGIC*r**(4d0/3d0)
|
|
endif
|
|
|
|
enddo
|
|
|
|
end subroutine RGIC_lda_exchange_energy
|