QuAcK/src/GW/GGW_phBSE.f90

subroutine GGW_phBSE(dophBSE2,TDA_W,TDA,dBSE,dTDA,eta,nBas,nC,nO,nV,nR,nS,ERI,dipole_int,eW,eGW,EcBSE)

! Compute the Bethe-Salpeter excitation energies

  implicit none
  include 'parameters.h'

! Input variables

  logical,intent(in)            :: dophBSE2
  logical,intent(in)            :: TDA_W
  logical,intent(in)            :: TDA
  logical,intent(in)            :: dBSE
  logical,intent(in)            :: dTDA

  double precision,intent(in)   :: eta
  integer,intent(in)            :: nBas
  integer,intent(in)            :: nC
  integer,intent(in)            :: nO
  integer,intent(in)            :: nV
  integer,intent(in)            :: nR
  integer,intent(in)            :: nS
  double precision,intent(in)   :: eW(nBas)
  double precision,intent(in)   :: eGW(nBas)
  double precision,intent(in)   :: ERI(nBas,nBas,nBas,nBas)
  double precision,intent(in)   :: dipole_int(nBas,nBas,ncart)

! Local variables

  logical                       :: dRPA   = .false.
  logical                       :: dRPA_W = .true.

  double precision              :: EcRPA
  double precision,allocatable  :: OmRPA(:)
  double precision,allocatable  :: XpY_RPA(:,:)
  double precision,allocatable  :: XmY_RPA(:,:)
  double precision,allocatable  :: rho_RPA(:,:,:)

  double precision,allocatable  :: OmBSE(:)
  double precision,allocatable  :: XpY_BSE(:,:)
  double precision,allocatable  :: XmY_BSE(:,:)

  double precision,allocatable  :: Aph(:,:)
  double precision,allocatable  :: Bph(:,:)

  double precision,allocatable  :: KA_sta(:,:)
  double precision,allocatable  :: KB_sta(:,:)

  double precision,allocatable  :: W(:,:,:,:)

! Output variables

  double precision,intent(out)  :: EcBSE

! Memory allocation

  allocate(OmRPA(nS),XpY_RPA(nS,nS),XmY_RPA(nS,nS),rho_RPA(nBas,nBas,nS), &
           Aph(nS,nS),Bph(nS,nS),KA_sta(nS,nS),KB_sta(nS,nS), &
           OmBSE(nS),XpY_BSE(nS,nS),XmY_BSE(nS,nS))

!---------------------------------
! Compute (singlet) RPA screening 
!---------------------------------

  EcRPA = 0d0

                 call phGLR_A(dRPA_W,nBas,nC,nO,nV,nR,nS,1d0,eW,ERI,Aph)
  if(.not.TDA_W) call phGLR_B(dRPA_W,nBas,nC,nO,nV,nR,nS,1d0,ERI,Bph)

  call phGLR(TDA_W,nS,Aph,Bph,EcRPA,OmRPA,XpY_RPA,XmY_RPA)
  call GGW_excitation_density(nBas,nC,nO,nR,nS,ERI,XpY_RPA,rho_RPA)

  call GGW_phBSE_static_kernel_A(eta,nBas,nC,nO,nV,nR,nS,1d0,ERI,OmRPA,rho_RPA,KA_sta)
  call GGW_phBSE_static_kernel_B(eta,nBas,nC,nO,nV,nR,nS,1d0,ERI,OmRPA,rho_RPA,KB_sta)


!-----!
! TDA !
!-----!

  if(TDA) then
    write(*,*) 'Tamm-Dancoff approximation activated in phBSE!'
    write(*,*)
  end if

!---------------------------------!
! Compute BSE excitation energies !
!---------------------------------!

  EcBSE = 0d0

               call phGLR_A(dRPA,nBas,nC,nO,nV,nR,nS,1d0,eGW,ERI,Aph)
  if(.not.TDA) call phGLR_B(dRPA,nBas,nC,nO,nV,nR,nS,1d0,ERI,Bph)

  ! Second-order BSE static kernel
 
! if(dophBSE2) then 

!   allocate(W(nBas,nBas,nBas,nBas))

!   write(*,*) 
!   write(*,*) '*** Second-order BSE static kernel activated! ***'
!   write(*,*) 

!   call GW_phBSE_static_kernel(eta,nBas,nC,nO,nV,nR,nS,1d0,ERI,OmRPA,rho_RPA,W)
!   call GW_phBSE2_static_kernel_A(eta,nBas,nC,nO,nV,nR,nS,1d0,eW,W,KA_sta)

!   if(.not.TDA) call GW_phBSE2_static_kernel_B(eta,nBas,nC,nO,nV,nR,nS,1d0,eW,W,KB_sta)

!   deallocate(W)

! end if

               Aph(:,:) = Aph(:,:) + KA_sta(:,:)
  if(.not.TDA) Bph(:,:) = Bph(:,:) + KB_sta(:,:)

  call phGLR(TDA,nS,Aph,Bph,EcBSE,OmBSE,XpY_BSE,XmY_BSE)

  call print_excitation_energies('phBSE@GW@GHF','spinorbital',nS,OmBSE)
  call phLR_transition_vectors(.true.,nBas,nC,nO,nV,nR,nS,dipole_int,OmBSE,XpY_BSE,XmY_BSE)

    !----------------------------------------------------!
    ! Compute the dynamical screening at the phBSE level !
    !----------------------------------------------------!

! if(dBSE) &
!     call GW_phBSE_dynamic_perturbation(dophBSE2,dTDA,eta,nBas,nC,nO,nV,nR,nS,eW,eGW,ERI,dipole_int,OmRPA,rho_RPA, &
!                                        OmBSE,XpY_BSE,XmY_BSE,KA_sta,KB_sta)

end subroutine