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mirror of https://github.com/pfloos/quack synced 2024-11-13 09:34:04 +01:00
quack/src/eDFT/UPBE_gga_exchange_potential.f90
2021-02-15 17:27:06 +01:00

68 lines
1.9 KiB
Fortran

subroutine UPBE_gga_exchange_potential(nGrid,weight,nBas,AO,dAO,rho,drho,Fx)
! Compute PBE GGA exchange potential
implicit none
include 'parameters.h'
! Input variables
integer,intent(in) :: nGrid
double precision,intent(in) :: weight(nGrid)
integer,intent(in) :: nBas
double precision,intent(in) :: AO(nBas,nGrid)
double precision,intent(in) :: dAO(3,nBas,nGrid)
double precision,intent(in) :: rho(nGrid)
double precision,intent(in) :: drho(3,nGrid)
! Local variables
integer :: mu,nu,iG
double precision :: mupbe,kappa
double precision :: r,g,s2,vAO,gAO
! Output variables
double precision,intent(out) :: Fx(nBas,nBas)
! Coefficients for PBE exchange functional
mupbe = ((1d0/2d0**(1d0/3d0))/(2d0*(3d0*pi**2)**(1d0/3d0)))**2*0.21951d0
kappa = 0.804d0
! Compute GGA exchange matrix in the AO basis
Fx(:,:) = 0d0
do mu=1,nBas
do nu=1,nBas
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
s2 = g/r**(8d0/3d0)
vAO = weight(iG)*AO(mu,iG)*AO(nu,iG)
Fx(mu,nu) = Fx(mu,nu) &
+ vAO*4d0/3d0*CxLSDA*r**(1d0/3d0)*(1d0 + kappa - kappa/(1d0 + mupbe*s2/kappa)) &
- vAO*8d0/3d0*CxLSDA*r**(1d0/3d0)*mupbe*s2/(1d0 + mupbe*s2/kappa)**2
gAO = drho(1,iG)*(dAO(1,mu,iG)*AO(nu,iG) + AO(mu,iG)*dAO(1,nu,iG)) &
+ drho(2,iG)*(dAO(2,mu,iG)*AO(nu,iG) + AO(mu,iG)*dAO(2,nu,iG)) &
+ drho(3,iG)*(dAO(3,mu,iG)*AO(nu,iG) + AO(mu,iG)*dAO(3,nu,iG))
gAO = weight(iG)*gAO
Fx(mu,nu) = Fx(mu,nu) + 2d0*gAO*CxLSDA*r**(-4d0/3d0)*mupbe/(1d0 + mupbe*s2/kappa)**2
end if
end do
end do
end do
end subroutine UPBE_gga_exchange_potential