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quack/src/eDFT/elda_correlation_potential.f90

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2020-03-31 22:15:45 +02:00
subroutine elda_correlation_potential(aLF,nGrid,weight,nBas,AO,rho,Fc)
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! Compute LDA correlation energy of 2-glomium for various states
implicit none
include 'parameters.h'
! Input variables
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double precision,intent(in) :: aLF(3)
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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) :: rho(nGrid,nspin)
! Local variables
integer :: mu,nu,iG
double precision :: ra,rb,r,ec_p
double precision :: dFcdra,dFcdrb
! Output variables
double precision,intent(out) :: Fc(nBas,nBas,nspin)
! Compute eLDA correlation potential
Fc(:,:,:) = 0d0
do mu=1,nBas
do nu=1,nBas
do iG=1,nGrid
ra = max(0d0,rho(iG,1))
rb = max(0d0,rho(iG,2))
if(ra > threshold) then
r = ra + rb
ec_p = aLF(1)/(1d0 + aLF(2)*r**(-1d0/6d0) + aLF(3)*r**(-1d0/3d0))
dFcdra = aLF(2)*r**(-1d0/6d0) + 2d0*aLF(3)*r**(-1d0/3d0)
dFcdra = dFcdra/(1d0 + aLF(2)*r**(-1d0/6d0) + aLF(3)*r**(-1d0/3d0))
dFcdra = ec_p*dFcdra/(6d0*r)
dFcdra = ec_p + dFcdra*r
Fc(mu,nu,1) = Fc(mu,nu,1) + weight(iG)*AO(mu,iG)*AO(nu,iG)*dFcdra
endif
if(rb > threshold) then
r = ra + rb
ec_p = aLF(1)/(1d0 + aLF(2)*r**(-1d0/6d0) + aLF(3)*r**(-1d0/3d0))
dFcdrb = aLF(2)*r**(-1d0/6d0) + 2d0*aLF(3)*r**(-1d0/3d0)
dFcdrb = dFcdrb/(1d0 + aLF(2)*r**(-1d0/6d0) + aLF(3)*r**(-1d0/3d0))
dFcdrb = ec_p*dFcdrb/(6d0*r)
dFcdrb = ec_p + dFcdrb*r
Fc(mu,nu,2) = Fc(mu,nu,2) + weight(iG)*AO(mu,iG)*AO(nu,iG)*dFcdrb
endif
end do
end do
end do
end subroutine elda_correlation_potential