2020-07-06 15:42:21 +02:00
|
|
|
subroutine US51_lda_exchange_energy(nGrid,weight,rho,Ex)
|
2019-03-13 11:07:31 +01:00
|
|
|
|
|
|
|
! Compute Slater's LDA exchange energy
|
|
|
|
|
|
|
|
implicit none
|
|
|
|
include 'parameters.h'
|
|
|
|
|
|
|
|
! Input variables
|
|
|
|
|
|
|
|
integer,intent(in) :: nGrid
|
|
|
|
double precision,intent(in) :: weight(nGrid)
|
|
|
|
double precision,intent(in) :: rho(nGrid)
|
|
|
|
|
|
|
|
! Local variables
|
|
|
|
|
|
|
|
integer :: iG
|
2020-07-02 14:27:38 +02:00
|
|
|
double precision :: alpha,r,alphaw,a2,b2,c2,a1,b1,c1
|
2019-03-13 11:07:31 +01:00
|
|
|
|
|
|
|
! Output variables
|
|
|
|
|
|
|
|
double precision :: Ex
|
|
|
|
|
2020-07-02 14:27:38 +02:00
|
|
|
! Cxw2 parameters for He N->N+1
|
|
|
|
! a2 = 0.135068d0
|
|
|
|
! b2 = -0.00774769d0
|
|
|
|
! c2 = -0.0278205d0
|
|
|
|
|
|
|
|
! Cxw1 parameters for He N->N-1
|
|
|
|
! a1 = 0.420243d0
|
|
|
|
! b1 = 0.0700561d0
|
|
|
|
! c1 = -0.288301d0
|
|
|
|
|
2019-03-13 11:07:31 +01:00
|
|
|
! Cx coefficient for Slater LDA exchange
|
|
|
|
|
|
|
|
alpha = -(3d0/2d0)*(3d0/(4d0*pi))**(1d0/3d0)
|
|
|
|
|
2020-07-02 14:27:38 +02:00
|
|
|
! alphaw = alpha*(1d0 - wEns(2)*(1d0 - wEns(2))*(a1 + b1*(wEns(2) - 0.5d0) + c1*(wEns(2) - 0.5d0)**2))
|
2019-03-13 11:07:31 +01:00
|
|
|
! Compute LDA exchange energy
|
|
|
|
|
|
|
|
Ex = 0d0
|
|
|
|
do iG=1,nGrid
|
|
|
|
|
|
|
|
r = max(0d0,rho(iG))
|
|
|
|
|
|
|
|
if(r > threshold) then
|
|
|
|
|
|
|
|
Ex = Ex + weight(iG)*alpha*r**(4d0/3d0)
|
|
|
|
|
|
|
|
endif
|
|
|
|
|
|
|
|
enddo
|
|
|
|
|
2020-07-02 14:27:38 +02:00
|
|
|
end subroutine US51_lda_exchange_energy
|