2019-02-04 23:51:09 +01:00
|
|
|
subroutine do_single_excitation(key_in,i_hole,i_particle,ispin,i_ok)
|
2019-01-25 11:39:31 +01:00
|
|
|
implicit none
|
|
|
|
|
BEGIN_DOC
|
|
|
|
|
! Apply the single excitation operator : a^{dager}_(i_particle) a_(i_hole) of spin = ispin
|
|
|
|
|
! on key_in
|
|
|
|
|
! ispin = 1 == alpha
|
|
|
|
|
! ispin = 2 == beta
|
|
|
|
|
! i_ok = 1 == the excitation is possible
|
|
|
|
|
! i_ok = -1 == the excitation is not possible
|
|
|
|
|
END_DOC
|
|
|
|
|
integer, intent(in) :: i_hole,i_particle,ispin
|
|
|
|
|
integer(bit_kind), intent(inout) :: key_in(N_int,2)
|
|
|
|
|
integer, intent(out) :: i_ok
|
|
|
|
|
integer :: k,j,i
|
|
|
|
|
use bitmasks
|
|
|
|
|
ASSERT (i_hole > 0 )
|
|
|
|
|
ASSERT (i_particle <= mo_num)
|
|
|
|
|
i_ok = 1
|
|
|
|
|
! hole
|
|
|
|
|
k = shiftr(i_hole-1,bit_kind_shift)+1
|
|
|
|
|
j = i_hole-shiftl(k-1,bit_kind_shift)-1
|
|
|
|
|
key_in(k,ispin) = ibclr(key_in(k,ispin),j)
|
|
|
|
|
|
|
|
|
|
! particle
|
|
|
|
|
k = shiftr(i_particle-1,bit_kind_shift)+1
|
|
|
|
|
j = i_particle-shiftl(k-1,bit_kind_shift)-1
|
|
|
|
|
key_in(k,ispin) = ibset(key_in(k,ispin),j)
|
|
|
|
|
integer :: n_elec_tmp
|
|
|
|
|
n_elec_tmp = 0
|
|
|
|
|
do i = 1, N_int
|
|
|
|
|
n_elec_tmp += popcnt(key_in(i,1)) + popcnt(key_in(i,2))
|
|
|
|
|
enddo
|
|
|
|
|
if(n_elec_tmp .ne. elec_num)then
|
|
|
|
|
!print*, n_elec_tmp,elec_num
|
|
|
|
|
!call debug_det(key_in,N_int)
|
|
|
|
|
i_ok = -1
|
|
|
|
|
endif
|
|
|
|
|
end
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
logical function is_spin_flip_possible(key_in,i_flip,ispin)
|
|
|
|
|
implicit none
|
|
|
|
|
BEGIN_DOC
|
|
|
|
|
! returns |true| if the spin-flip of spin ispin in the orbital i_flip is possible
|
|
|
|
|
! on key_in
|
|
|
|
|
END_DOC
|
|
|
|
|
integer, intent(in) :: i_flip,ispin
|
|
|
|
|
integer(bit_kind), intent(in) :: key_in(N_int,2)
|
|
|
|
|
integer :: k,j,i
|
|
|
|
|
integer(bit_kind) :: key_tmp(N_int,2)
|
|
|
|
|
is_spin_flip_possible = .False.
|
|
|
|
|
key_tmp = 0_bit_kind
|
|
|
|
|
k = shiftr(i_flip-1,bit_kind_shift)+1
|
|
|
|
|
j = i_flip-shiftl(k-1,bit_kind_shift)-1
|
|
|
|
|
key_tmp(k,1) = ibset(key_tmp(k,1),j)
|
|
|
|
|
integer :: other_spin(2)
|
|
|
|
|
other_spin(1) = 2
|
|
|
|
|
other_spin(2) = 1
|
|
|
|
|
if(popcnt(iand(key_tmp(k,1),key_in(k,ispin))) == 1 .and. popcnt(iand(key_tmp(k,1),key_in(k,other_spin(ispin)))) == 0 )then
|
|
|
|
|
! There is a spin "ispin" in the orbital i_flip AND There is no electron of opposit spin in the same orbital "i_flip"
|
|
|
|
|
is_spin_flip_possible = .True.
|
|
|
|
|
return
|
|
|
|
|
else
|
|
|
|
|
return
|
|
|
|
|
endif
|
|
|
|
|
end
|
|
|
|
|
|
