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https://github.com/pfloos/quack
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102 lines
3.5 KiB
Fortran
102 lines
3.5 KiB
Fortran
recursive function HRR2e(AngMomBra,AngMomKet, &
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maxm,Om,ExpZi,ExpY, &
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CenterAB,CenterZA,CenterY) &
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result(a1a2b1b2)
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! Horintal recurrence relations for two-electron integrals
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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) :: AngMomBra(2,3),AngMomKet(2,3)
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integer,intent(in) :: maxm
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double precision,intent(in) :: Om(0:maxm),ExpZi(2),ExpY(2,2)
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double precision,intent(in) :: CenterAB(2,3),CenterZA(2,3),CenterY(2,2,3)
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! Local variables
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logical :: NegAngMomKet(2)
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integer :: TotAngMomBra(2),TotAngMomKet(2)
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integer :: a1p(2,3),b1m(2,3),a2p(2,3),b2m(2,3)
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integer :: i,j,xyz
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double precision :: VRR2e
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! Output variables
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double precision :: a1a2b1b2
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do i=1,2
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NegAngMomKet(i) = AngMomKet(i,1) < 0 .or. AngMomKet(i,2) < 0 .or. AngMomKet(i,3) < 0
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TotAngMomBra(i) = AngMomBra(i,1) + AngMomBra(i,2) + AngMomBra(i,3)
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TotAngMomKet(i) = AngMomKet(i,1) + AngMomKet(i,2) + AngMomKet(i,3)
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end do
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!------------------------------------------------------------------------
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! Termination condition
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!------------------------------------------------------------------------
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! if(NegAngMomKet(1) .or. NegAngMomKet(2)) then
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! a1a2b1b2 = 0d0
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!------------------------------------------------------------------------
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! 1st and 2nd vertical recurrence relations: <a1a2|00>
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!------------------------------------------------------------------------
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! elseif(TotAngMomKet(1) == 0 .and. TotAngMomKet(2) == 0) then
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if(TotAngMomKet(1) == 0 .and. TotAngMomKet(2) == 0) then
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a1a2b1b2 = VRR2e(0,AngMomBra,maxm,Om,ExpZi,ExpY,CenterZA,CenterY)
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!------------------------------------------------------------------------
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! 1st horizontal recurrence relation (2 terms): <a1a2|b1+0>
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!------------------------------------------------------------------------
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elseif(TotAngMomKet(2) == 0) then
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do i=1,2
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do j=1,3
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a1p(i,j) = AngMomBra(i,j)
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b1m(i,j) = AngMomKet(i,j)
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end do
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end do
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! Loop over cartesian directions
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xyz = 0
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if (AngMomKet(1,1) > 0) then
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xyz = 1
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elseif(AngMomKet(1,2) > 0) then
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xyz = 2
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elseif(AngMomKet(1,3) > 0) then
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xyz = 3
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else
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write(*,*) 'xyz = 0 in HRR2e!'
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end if
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! End loop over cartesian directions
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a1p(1,xyz) = a1p(1,xyz) + 1
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b1m(1,xyz) = b1m(1,xyz) - 1
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a1a2b1b2 = HRR2e(a1p,b1m,maxm,Om,ExpZi,ExpY,CenterAB,CenterZA,CenterY) &
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+ CenterAB(1,xyz)*HRR2e(AngMomBra,b1m,maxm,Om,ExpZi,ExpY,CenterAB,CenterZA,CenterY)
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!------------------------------------------------------------------------
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! 2nd horizontal recurrence relation (2 terms): <a1a2|b1b2+>
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!------------------------------------------------------------------------
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else
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do i=1,2
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do j=1,3
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a2p(i,j) = AngMomBra(i,j)
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b2m(i,j) = AngMomKet(i,j)
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end do
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end do
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! Loop over cartesian directions
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xyz = 0
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if (AngMomKet(2,1) > 0) then
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xyz = 1
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elseif(AngMomKet(2,2) > 0) then
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xyz = 2
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elseif(AngMomKet(2,3) > 0) then
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xyz = 3
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else
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write(*,*) 'xyz = 0 in HRR2e!'
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end if
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! End loop over cartesian directions
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a2p(2,xyz) = a2p(2,xyz) + 1
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b2m(2,xyz) = b2m(2,xyz) - 1
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a1a2b1b2 = HRR2e(a2p,b2m,maxm,Om,ExpZi,ExpY,CenterAB,CenterZA,CenterY) &
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+ CenterAB(2,xyz)*HRR2e(AngMomBra,b2m,maxm,Om,ExpZi,ExpY,CenterAB,CenterZA,CenterY)
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end if
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end function HRR2e
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