mirror of https://github.com/pfloos/quack
77 lines
2.3 KiB
Fortran
77 lines
2.3 KiB
Fortran
recursive function VRRNuc(m,AngMomA,maxm,Om,ExpPi,CenterAB,CenterPA,CenterPC) &
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result(Ga)
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! Compute two-electron integrals over Gaussian geminals
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implicit none
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! Input variables
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integer,intent(in) :: m
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integer,intent(in) :: AngMomA(3)
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integer,intent(in) :: maxm
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double precision,intent(in) :: Om(0:maxm)
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double precision,intent(in) :: ExpPi
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double precision,intent(in) :: CenterAB(3),CenterPA(3),CenterPC(3)
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! Local variables
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logical :: NegAngMomA
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integer :: TotAngMomA
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integer :: xyz,am(3),amm(3)
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integer :: i
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! Output variables
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double precision :: Ga
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NegAngMomA = AngMomA(1) < 0 .or. AngMomA(2) < 0 .or. AngMomA(3) < 0
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TotAngMomA = AngMomA(1) + AngMomA(2) + AngMomA(3)
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!------------------------------------------------------------------------
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! Termination condition
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!------------------------------------------------------------------------
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if(NegAngMomA) then
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Ga = 0d0
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else
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!------------------------------------------------------------------------
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! Fundamental integral: (0|0)^m
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!------------------------------------------------------------------------
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if(TotAngMomA == 0) then
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Ga = Om(m)
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else
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!------------------------------------------------------------------------
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! Vertical recurrence relation (4 terms): (a+|0)^m
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!------------------------------------------------------------------------
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do i=1,3
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am(i) = AngMomA(i)
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amm(i) = AngMomA(i)
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enddo
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! Loop over cartesian directions
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xyz = 0
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if (AngMomA(1) > 0) then
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xyz = 1
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elseif(AngMomA(2) > 0) then
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xyz = 2
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elseif(AngMomA(3) > 0) then
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xyz = 3
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else
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write(*,*) 'xyz = 0 in VRRNuc!'
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endif
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! End loop over cartesian directions
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am(xyz) = am(xyz) - 1
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amm(xyz) = amm(xyz) - 2
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Ga = CenterPA(xyz)*VRRNuc(m,am,maxm,Om,ExpPi,CenterAB,CenterPA,CenterPC) &
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+ 0.5d0*dble(am(xyz))*ExpPi*VRRNuc(m,amm,maxm,Om,ExpPi,CenterAB,CenterPA,CenterPC) &
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- CenterPC(xyz)*ExpPi*VRRNuc(m+1,am,maxm,Om,ExpPi,CenterAB,CenterPA,CenterPC) &
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- 0.5d0*dble(am(xyz))*ExpPi**2*VRRNuc(m+1,amm,maxm,Om,ExpPi,CenterAB,CenterPA,CenterPC)
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endif
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endif
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end function VRRNuc
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