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https://github.com/LCPQ/quantum_package
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37 lines
1.0 KiB
Fortran
37 lines
1.0 KiB
Fortran
subroutine do_mono_excitation(key_in,i_hole,i_particle,ispin,i_ok)
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implicit none
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BEGIN_DOC
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! Apply the mono excitation operator : a^{dager}_(i_particle) a_(i_hole) of spin = ispin
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! on key_in
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! ispin = 1 == alpha
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! ispin = 2 == beta
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! i_ok = 1 == the excitation is possible
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! i_ok = -1 == the excitation is not possible
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END_DOC
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integer, intent(in) :: i_hole,i_particle,ispin
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integer(bit_kind), intent(inout) :: key_in(N_int,2)
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integer, intent(out) :: i_ok
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integer :: k,j,i
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use bitmasks
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ASSERT (i_hole > 0 )
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ASSERT (i_particle <= mo_tot_num)
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i_ok = 1
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! hole
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k = ishft(i_hole-1,-bit_kind_shift)+1
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j = i_hole-ishft(k-1,bit_kind_shift)-1
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key_in(k,ispin) = ibclr(key_in(k,ispin),j)
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! particle
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k = ishft(i_particle-1,-bit_kind_shift)+1
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j = i_particle-ishft(k-1,bit_kind_shift)-1
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key_in(k,ispin) = ibset(key_in(k,ispin),j)
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integer :: n_elec_tmp
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n_elec_tmp = 0
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do i = 1, N_int
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n_elec_tmp += popcnt(key_in(i,1)) + popcnt(key_in(i,2))
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enddo
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if(n_elec_tmp .ne. elec_num)then
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i_ok = -1
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endif
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end
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