mirror of
https://github.com/pfloos/quack
synced 2025-05-06 23:34:42 +02:00
154 lines
3.3 KiB
Fortran
154 lines
3.3 KiB
Fortran
subroutine UGW_phBSE_static_kernel_B(ispin,eta,nBas,nC,nO,nV,nR,nSa,nSb,nSt,nS_sc,lambda,Om,rho,KB)
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! Compute the extra term for Bethe-Salpeter equation for linear response
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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) :: ispin
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integer,intent(in) :: nBas
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integer,intent(in) :: nC(nspin)
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integer,intent(in) :: nO(nspin)
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integer,intent(in) :: nV(nspin)
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integer,intent(in) :: nR(nspin)
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integer,intent(in) :: nSa
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integer,intent(in) :: nSb
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integer,intent(in) :: nSt
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integer,intent(in) :: nS_sc
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double precision,intent(in) :: eta
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double precision,intent(in) :: lambda
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double precision,intent(in) :: Om(nS_sc)
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double precision,intent(in) :: rho(nBas,nBas,nS_sc,nspin)
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! Local variables
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double precision :: chi
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double precision :: eps
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integer :: i,j,a,b,ia,jb,kc
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! Output variables
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double precision,intent(out) :: KB(nSt,nSt)
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! Initialization
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KB(:,:) = 0d0
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!--------------------------------------------------!
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! Build BSE matrix for spin-conserving transitions !
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!--------------------------------------------------!
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if(ispin == 1) then
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! aaaa block
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ia = 0
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do i=nC(1)+1,nO(1)
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do a=nO(1)+1,nBas-nR(1)
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ia = ia + 1
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jb = 0
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do j=nC(1)+1,nO(1)
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do b=nO(1)+1,nBas-nR(1)
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jb = jb + 1
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chi = 0d0
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do kc=1,nS_sc
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eps = Om(kc)**2 + eta**2
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chi = chi + rho(i,b,kc,1)*rho(a,j,kc,1)*Om(kc)/eps
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end do
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KB(ia,jb) = 2d0*lambda**2*chi
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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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! bbbb block
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ia = 0
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do i=nC(2)+1,nO(2)
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do a=nO(2)+1,nBas-nR(2)
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ia = ia + 1
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jb = 0
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do j=nC(2)+1,nO(2)
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do b=nO(2)+1,nBas-nR(2)
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jb = jb + 1
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chi = 0d0
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do kc=1,nS_sc
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eps = Om(kc)**2 + eta**2
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chi = chi + rho(i,b,kc,2)*rho(a,j,kc,2)*Om(kc)/eps
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end do
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KB(nSa+ia,nSa+jb) = 2d0*lambda**2*chi
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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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end if
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!--------------------------------------------!
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! Build BSE matrix for spin-flip transitions !
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!--------------------------------------------!
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if(ispin == 2) then
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! abba block
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ia = 0
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do i=nC(1)+1,nO(1)
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do a=nO(2)+1,nBas-nR(2)
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ia = ia + 1
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jb = 0
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do j=nC(2)+1,nO(2)
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do b=nO(1)+1,nBas-nR(1)
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jb = jb + 1
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chi = 0d0
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do kc=1,nS_sc
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eps = Om(kc)**2 + eta**2
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chi = chi + rho(i,b,kc,1)*rho(a,j,kc,2)*Om(kc)/eps
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end do
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KB(ia,nSa+jb) = 2d0*lambda**2*chi
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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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! baab block
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ia = 0
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do i=nC(2)+1,nO(2)
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do a=nO(1)+1,nBas-nR(1)
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ia = ia + 1
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jb = 0
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do j=nC(1)+1,nO(1)
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do b=nO(2)+1,nBas-nR(2)
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jb = jb + 1
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chi = 0d0
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do kc=1,nS_sc
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eps = Om(kc)**2 + eta**2
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chi = chi + rho(i,b,kc,2)*rho(a,j,kc,1)*Om(kc)/eps
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end do
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KB(nSa+ia,jb) = 2d0*lambda**2*chi
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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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end if
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end subroutine
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