quack/src/RPA/phURPAx.f90

subroutine phURPAx(TDA,doACFDT,exchange_kernel,spin_conserved,spin_flip,nBas,nC,nO,nV,nR,nS,ENuc,EUHF, & 
                   ERI_aaaa,ERI_aabb,ERI_bbbb,dipole_int_aa,dipole_int_bb,e,c,S)

! Perform random phase approximation calculation with exchange (aka TDHF) in the unrestricted formalism

  implicit none
  include 'parameters.h'
  include 'quadrature.h'

! Input variables

  logical,intent(in)            :: TDA
  logical,intent(in)            :: doACFDT
  logical,intent(in)            :: exchange_kernel
  logical,intent(in)            :: spin_conserved
  logical,intent(in)            :: spin_flip
  integer,intent(in)            :: nBas
  integer,intent(in)            :: nC(nspin)
  integer,intent(in)            :: nO(nspin)
  integer,intent(in)            :: nV(nspin)
  integer,intent(in)            :: nR(nspin)
  integer,intent(in)            :: nS(nspin)
  double precision,intent(in)   :: ENuc
  double precision,intent(in)   :: EUHF
  double precision,intent(in)   :: e(nBas,nspin)
  double precision,intent(in)   :: c(nBas,nBas,nspin)
  double precision,intent(in)   :: S(nBas,nBas)
  double precision,intent(in)   :: ERI_aaaa(nBas,nBas,nBas,nBas)
  double precision,intent(in)   :: ERI_aabb(nBas,nBas,nBas,nBas)
  double precision,intent(in)   :: ERI_bbbb(nBas,nBas,nBas,nBas)
  double precision,intent(in)   :: dipole_int_aa(nBas,nBas,ncart)
  double precision,intent(in)   :: dipole_int_bb(nBas,nBas,ncart)

! Local variables

  logical                       :: dRPA
  integer                       :: ispin

  integer                       :: nSa,nSb,nSt
  double precision,allocatable  :: Aph(:,:)
  double precision,allocatable  :: Bph(:,:)
  double precision,allocatable  :: Om(:)
  double precision,allocatable  :: XpY(:,:)
  double precision,allocatable  :: XmY(:,:)

  double precision              :: rho
  double precision              :: EcRPA(nspin)

! Hello world

  write(*,*)
  write(*,*)'************************************'
  write(*,*)'* Unrestricted ph-RPAx Calculation *'
  write(*,*)'************************************'
  write(*,*)

! TDA 

  if(TDA) then
    write(*,*) 'Tamm-Dancoff approximation activated!'
    write(*,*) ' => RPAx + TDA = CIS '
    write(*,*)
  end if

! Initialization

  dRPA = .false.
  EcRPA(:) = 0d0

! Spin-conserved transitions

  if(spin_conserved) then

    ispin = 1

    ! Memory allocation

    nSa = nS(1)
    nSb = nS(2)
    nSt = nSa + nSb

    allocate(Aph(nSt,nSt),Bph(nSt,nSt),Om(nSt),XpY(nSt,nSt),XmY(nSt,nSt))

    call phULR_A(ispin,dRPA,nBas,nC,nO,nV,nR,nSa,nSb,nSt,1d0,e,ERI_aaaa,ERI_aabb,ERI_bbbb,Aph)
    if(.not.TDA) call phULR_B(ispin,dRPA,nBas,nC,nO,nV,nR,nSa,nSb,nSt,1d0,ERI_aaaa,ERI_aabb,ERI_bbbb,Bph)

    call phULR(TDA,nSa,nSb,nSt,Aph,Bph,EcRPA(ispin),Om,XpY,XmY)
    call print_excitation_energies('phRPA@UHF',5,nSt,Om)
    call phULR_transition_vectors(ispin,nBas,nC,nO,nV,nR,nS,nSa,nSb,nSt,dipole_int_aa,dipole_int_bb,c,S,Om,XpY,XmY)

    deallocate(Aph,Bph,Om,XpY,XmY)

  endif

! Spin-flip transitions

  if(spin_flip) then

    ispin = 2

    ! Memory allocation

    nSa = (nO(1) - nC(1))*(nV(2) - nR(2))
    nSb = (nO(2) - nC(2))*(nV(1) - nR(1))
    nSt = nSa + nSb

    allocate(Om(nSt),XpY(nSt,nSt),XmY(nSt,nSt))

    call phULR_A(ispin,dRPA,nBas,nC,nO,nV,nR,nSa,nSb,nSt,1d0,e,ERI_aaaa,ERI_aabb,ERI_bbbb,Aph)
    if(.not.TDA) call phULR_B(ispin,dRPA,nBas,nC,nO,nV,nR,nSa,nSb,nSt,1d0,ERI_aaaa,ERI_aabb,ERI_bbbb,Bph)

    call phULR(TDA,nSa,nSa,nSt,Aph,Bph,EcRPA(ispin),Om,XpY,XmY)
    call print_excitation_energies('phRPA@UHF',6,nSt,Om)
    call phULR_transition_vectors(ispin,nBas,nC,nO,nV,nR,nS,nSa,nSb,nSt,dipole_int_aa,dipole_int_bb,c,S,Om,XpY,XmY)

    deallocate(Aph,Bph,Om,XpY,XmY)

  endif

  if(exchange_kernel) then

    EcRPA(1) = 0.5d0*EcRPA(1)
    EcRPA(2) = 1.5d0*EcRPA(2)

  end if

  if(exchange_kernel) then

    EcRPA(1) = 0.5d0*EcRPA(1)
    EcRPA(2) = 0.5d0*EcRPA(2)

  else

    EcRPA(2) = 0d0

  end if

  write(*,*)
  write(*,*)'-------------------------------------------------------------------------------'
  write(*,'(2X,A50,F20.10)') 'Tr@URPAx correlation energy (spin-conserved) =',EcRPA(1)
  write(*,'(2X,A50,F20.10)') 'Tr@URPAx correlation energy (spin-flip)      =',EcRPA(2)
  write(*,'(2X,A50,F20.10)') 'Tr@URPAx correlation energy                  =',EcRPA(1) + EcRPA(2)
  write(*,'(2X,A50,F20.10)') 'Tr@URPAx total energy                        =',ENuc + EUHF + EcRPA(1) + EcRPA(2)
  write(*,*)'-------------------------------------------------------------------------------'
  write(*,*)

! Compute the correlation energy via the adiabatic connection 

  if(doACFDT) then

    write(*,*) '----------------------------------------------------------'
    write(*,*) ' Adiabatic connection version of URPAx correlation energy '
    write(*,*) '----------------------------------------------------------'
    write(*,*)

    call phUACFDT(exchange_kernel,.false.,.false.,.false.,TDA,.false.,spin_conserved,spin_flip, &
                  nBas,nC,nO,nV,nR,nS,ERI_aaaa,ERI_aabb,ERI_bbbb,e,e,EcRPA)

    write(*,*)
    write(*,*)'-------------------------------------------------------------------------------'
    write(*,'(2X,A50,F20.10)') 'AC@URPAx correlation energy (spin-conserved) =',EcRPA(1)
    write(*,'(2X,A50,F20.10)') 'AC@URPAx correlation energy (spin-flip)      =',EcRPA(2)
    write(*,'(2X,A50,F20.10)') 'AC@URPAx correlation energy                  =',EcRPA(1) + EcRPA(2)
    write(*,'(2X,A50,F20.10)') 'AC@URPAx total energy                        =',ENuc + EUHF + EcRPA(1) + EcRPA(2)
    write(*,*)'-------------------------------------------------------------------------------'
    write(*,*)

  end if

end subroutine