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