mirror of
https://github.com/pfloos/quack
synced 2024-12-25 22:03:44 +01:00
95 lines
1.9 KiB
Fortran
95 lines
1.9 KiB
Fortran
subroutine RCC_lda_exchange_energy(nEns,wEns,aCC_w1,aCC_w2,nGrid,weight,rho,Ex,Cx_choice)
|
|
|
|
! Compute the restricted version of the curvature-corrected exchange functional
|
|
|
|
implicit none
|
|
include 'parameters.h'
|
|
|
|
! Input variables
|
|
|
|
integer,intent(in) :: nEns
|
|
double precision,intent(in) :: wEns(nEns)
|
|
double precision,intent(in) :: aCC_w1(3)
|
|
double precision,intent(in) :: aCC_w2(3)
|
|
integer,intent(in) :: nGrid
|
|
double precision,intent(in) :: weight(nGrid)
|
|
double precision,intent(in) :: rho(nGrid)
|
|
integer,intent(in) :: Cx_choice
|
|
|
|
! Local variables
|
|
|
|
integer :: iG
|
|
double precision :: r
|
|
|
|
double precision :: a1,b1,c1,w1
|
|
double precision :: a2,b2,c2,w2
|
|
double precision :: Fx1,Fx2,Cx
|
|
|
|
! Output variables
|
|
|
|
double precision :: Ex
|
|
|
|
! Single excitation parameter
|
|
|
|
! a1 = 0.0d0
|
|
! b1 = 0.0d0
|
|
! c1 = 0.0d0
|
|
|
|
! Parameters for H2 at equilibrium
|
|
|
|
! a2 = +0.5751782560799208d0
|
|
! b2 = -0.021108186591137282d0
|
|
! c2 = -0.36718902716347124d0
|
|
|
|
! Parameters for stretch H2
|
|
|
|
! a2 = + 0.01922622507087411d0
|
|
! b2 = - 0.01799647558018601d0
|
|
! c2 = - 0.022945430666782573d0
|
|
|
|
! Parameters for He
|
|
|
|
! a2 = 1.9125735895875828d0
|
|
! b2 = 2.715266992840757d0
|
|
! c2 = 2.1634223380633086d0
|
|
|
|
a1 = aCC_w1(1)
|
|
b1 = aCC_w1(2)
|
|
c1 = aCC_w1(3)
|
|
|
|
a2 = aCC_w2(1)
|
|
b2 = aCC_w2(2)
|
|
c2 = aCC_w2(3)
|
|
|
|
|
|
w1 = wEns(2)
|
|
Fx1 = 1d0 - w1*(1d0 - w1)*(a1 + b1*(w1 - 0.5d0) + c1*(w1 - 0.5d0)**2)
|
|
|
|
w2 = wEns(3)
|
|
Fx2 = 1d0 - w2*(1d0 - w2)*(a2 + b2*(w2 - 0.5d0) + c2*(w2 - 0.5d0)**2)
|
|
|
|
select case (Cx_choice)
|
|
case(1)
|
|
Cx = CxLDA*Fx1
|
|
case(2)
|
|
Cx = CxLDA*Fx2
|
|
case(3)
|
|
Cx = CxLDA*Fx2*Fx1
|
|
end select
|
|
|
|
! Compute GIC-LDA exchange energy
|
|
|
|
Ex = 0d0
|
|
|
|
do iG=1,nGrid
|
|
|
|
r = max(0d0,rho(iG))
|
|
|
|
if(r > threshold) then
|
|
Ex = Ex + weight(iG)*Cx*r**(4d0/3d0)
|
|
endif
|
|
|
|
enddo
|
|
|
|
end subroutine RCC_lda_exchange_energy
|