mirror of https://github.com/pfloos/quack
72 lines
2.3 KiB
Fortran
72 lines
2.3 KiB
Fortran
recursive function HRRNuc(AngMomA,AngMomB,maxm,Om,ExpPi,CenterAB,CenterPA,CenterPC) &
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result(Gab)
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! Horizontal recurrence relation for one-electron nuclear attraction integrals
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implicit none
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! Input variables
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integer,intent(in) :: AngMomA(3),AngMomB(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 :: NegAngMomB
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integer :: TotAngMomA,TotAngMomB
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integer :: xyz,ap(3),bm(3)
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integer :: i
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double precision :: VRRNuc
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! Output variables
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double precision :: Gab
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NegAngMomB = AngMomB(1) < 0 .or. AngMomB(2) < 0 .or. AngMomB(3) < 0
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TotAngMomA = AngMomA(1) + AngMomA(2) + AngMomA(3)
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TotAngMomB = AngMomB(1) + AngMomB(2) + AngMomB(3)
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!------------------------------------------------------------------------
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! Termination condition
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!------------------------------------------------------------------------
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if(NegAngMomB) then
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Gab = 0d0
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else
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!------------------------------------------------------------------------
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! Vertical recurrence relations: (a|0)
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!------------------------------------------------------------------------
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if(TotAngMomB == 0) then
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Gab = VRRNuc(0,AngMomA,maxm,Om,ExpPi,CenterAB,CenterPA,CenterPC)
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else
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!------------------------------------------------------------------------
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! 1st horizontal recurrence relation (2 terms): (a|b+)
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!------------------------------------------------------------------------
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do i=1,3
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ap(i) = AngMomA(i)
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bm(i) = AngMomB(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 (AngMomB(1) > 0) then
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xyz = 1
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elseif(AngMomB(2) > 0) then
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xyz = 2
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elseif(AngMomB(3) > 0) then
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xyz = 3
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else
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write(*,*) 'xyz = 0 in HRRNuc!'
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endif
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! End loop over cartesian directions
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ap(xyz) = ap(xyz) + 1
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bm(xyz) = bm(xyz) - 1
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Gab = HRRNuc(ap,bm,maxm,Om,ExpPi,CenterAB,CenterPA,CenterPC) &
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+ CenterAB(xyz)*HRRNuc(AngMomA,bm,maxm,Om,ExpPi,CenterAB,CenterPA,CenterPC)
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endif
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endif
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end function HRRNuc
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