mirror of
https://github.com/pfloos/quack
synced 2024-06-26 15:12:17 +02:00
101 lines
2.0 KiB
Fortran
101 lines
2.0 KiB
Fortran
subroutine CC_B88_gga_exchange_energy(nEns,wEns,nCC,aCC,nGrid,weight,&
|
|
rho,drho,Cx_choice,Ex)
|
|
|
|
! Compute the unrestricted version of the curvature-corrected exchange functional
|
|
|
|
implicit none
|
|
include 'parameters.h'
|
|
|
|
! Input variables
|
|
|
|
integer,intent(in) :: nEns
|
|
double precision,intent(in) :: wEns(nEns)
|
|
integer,intent(in) :: nCC
|
|
double precision,intent(in) :: aCC(nCC,nEns-1)
|
|
integer,intent(in) :: nGrid
|
|
double precision,intent(in) :: weight(nGrid)
|
|
double precision,intent(in) :: rho(nGrid)
|
|
double precision,intent(in) :: drho(3,nGrid)
|
|
integer,intent(in) :: Cx_choice
|
|
|
|
! Local variables
|
|
|
|
integer :: iG
|
|
double precision :: b
|
|
double precision :: r,g,x
|
|
|
|
double precision :: a1,b1,c1,d1,w1
|
|
double precision :: a2,b2,c2,d2,w2
|
|
double precision :: Fx1,Fx2,Cx
|
|
|
|
! Output variables
|
|
|
|
double precision :: Ex
|
|
|
|
! Coefficients for B88 GGA exchange functional
|
|
|
|
b = 0.0042d0
|
|
|
|
! Defining enhancements factor for weight-dependent functionals
|
|
|
|
! Parameters for first state
|
|
|
|
a1 = aCC(1,1)
|
|
b1 = aCC(2,1)
|
|
c1 = aCC(3,1)
|
|
d1 = aCC(4,1)
|
|
|
|
! Parameters for second state
|
|
|
|
a2 = aCC(1,2)
|
|
b2 = aCC(2,2)
|
|
c2 = aCC(3,2)
|
|
d2 = aCC(4,2)
|
|
|
|
|
|
w1 = wEns(2)
|
|
Fx1 = 1d0 + a1*w1 + b1*w1**2 + c1*w1**3 + d1*w1**4
|
|
|
|
w2 = wEns(3)
|
|
Fx2 = 1d0 + a2*w2 + b2*w2**2 + c2*w2**3 + d2*w2**4
|
|
|
|
|
|
select case (Cx_choice)
|
|
|
|
case(1)
|
|
Cx = Fx1
|
|
|
|
case(2)
|
|
Cx = Fx2
|
|
|
|
case(3)
|
|
Cx = Fx2*Fx1
|
|
|
|
case default
|
|
Cx = 1.d0
|
|
|
|
end select
|
|
|
|
|
|
! Compute GIC-GGA exchange energy
|
|
|
|
Ex = 0d0
|
|
|
|
do iG=1,nGrid
|
|
|
|
r = max(0d0,rho(iG))
|
|
|
|
if(r > threshold) then
|
|
g = drho(1,iG)**2 + drho(2,iG)**2 + drho(3,iG)**2
|
|
x = sqrt(g)/r**(4d0/3d0)
|
|
|
|
Ex = Ex + weight(iG)*r**(4d0/3d0)*(CxLSDA - b*x**2/(1d0 + 6d0*b*x*asinh(x)))
|
|
|
|
end if
|
|
|
|
end do
|
|
|
|
Ex = Cx*Ex
|
|
|
|
end subroutine CC_B88_gga_exchange_energy
|