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https://github.com/pfloos/quack
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100 lines
2.1 KiB
Fortran
100 lines
2.1 KiB
Fortran
subroutine G0F2(linearize,nBas,nC,nO,nV,nR,V,e0)
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! Perform a one-shot second-order Green function calculation
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implicit none
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include 'parameters.h'
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! Input variables
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logical,intent(in) :: linearize
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integer,intent(in) :: nBas
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integer,intent(in) :: nO
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integer,intent(in) :: nC
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integer,intent(in) :: nV
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integer,intent(in) :: nR
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double precision,intent(in) :: e0(nBas)
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double precision,intent(in) :: V(nBas,nBas,nBas,nBas)
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! Local variables
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double precision :: eps
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double precision :: VV
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double precision,allocatable :: eGF2(:)
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double precision,allocatable :: Sig(:)
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double precision,allocatable :: Z(:)
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integer :: i,j,a,b,p
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! Hello world
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write(*,*)
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write(*,*)'************************************************'
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write(*,*)'| One-shot second-order Green function |'
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write(*,*)'************************************************'
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write(*,*)
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! Memory allocation
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allocate(Sig(nBas),Z(nBas),eGF2(nBas))
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if(linearize) then
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write(*,*) '*** Quasiparticle equation will be linearized ***'
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write(*,*)
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end if
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! Frequency-dependent second-order contribution
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Sig(:) = 0d0
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Z(:) = 0d0
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do p=nC+1,nBas-nR
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do i=nC+1,nO
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do j=nC+1,nO
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do a=nO+1,nBas-nR
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eps = e0(p) + e0(a) - e0(i) - e0(j)
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VV = (2d0*V(p,a,i,j) - V(p,a,j,i))*V(p,a,i,j)
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Sig(p) = Sig(p) + VV/eps
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Z(p) = Z(p) + VV/eps**2
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end do
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end do
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end do
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end do
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do p=nC+1,nBas-nR
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do i=nC+1,nO
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do a=nO+1,nBas-nR
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do b=nO+1,nBas-nR
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eps = e0(p) + e0(i) - e0(a) - e0(b)
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VV = (2d0*V(p,i,a,b) - V(p,i,b,a))*V(p,i,a,b)
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Sig(p) = Sig(p) + VV/eps
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Z(p) = Z(p) + VV/eps**2
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end do
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end do
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end do
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end do
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Z(:) = 1d0/(1d0 + Z(:))
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if(linearize) then
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eGF2(:) = e0(:) + Z(:)*Sig(:)
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else
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eGF2(:) = e0(:) + Sig(:)
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end if
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! Print results
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call print_G0F2(nBas,nO,e0,Sig,eGF2,Z)
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end subroutine G0F2
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