166 lines
6.1 KiB
Fortran
166 lines
6.1 KiB
Fortran
subroutine example_determinants
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use bitmasks ! you need to include the bitmasks_module.f90 features
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implicit none
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BEGIN_DOC
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! subroutine that illustrates the main features available in determinants
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END_DOC
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print*,'a determinant is stored as a binary representation of the occupancy of the spatial orbitals'
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print*,'see the bitmask module for more information about that '
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print*,'a spin determinant is an array of (N_int) integers of type bit_kind (see bitmask for more information)'
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print*,'A determinant containing alpha and beta electrons is an array of dimension (2,N_int)'
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integer(bit_kind), allocatable :: det_i(:,:)
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allocate(det_i(N_int,2))
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print*,'det_i(1,:) alpha spins '
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print*,'det_i(2,:) beta spins '
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integer :: i,j
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print*,'initialize det_i to an electron occupation corresponding RHF or ROHF: ref_bitmask '
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do i = 1, N_int
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det_i(i,1) = ref_bitmask(i,1)
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det_i(i,2) = ref_bitmask(i,2)
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enddo
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print*,''
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print*,'print a human readable representation of the determinant '
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call print_det(det_i,N_int)
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print*,'doing a single excitation on top of det_i'
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integer :: h1,p1,s1,i_ok
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h1 = 1
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p1 = elec_alpha_num + 1
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s1 = 1
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print*,'h1 --> p1 of spin s1'
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print*,'i_ok == +1 : excitation is possible '
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print*,'i_ok == -1 : excitation is NOT possible '
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call do_single_excitation(det_i,h1,p1,s1,i_ok)
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print*,'h1,p1,s1,i_ok'
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print*, h1,p1,s1,i_ok
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if(i_ok == -1)then
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print*,'excitation was not possible '
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stop
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endif
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call debug_det(det_i,N_int)
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print*,'computing the interaction between ref_determinant and det_i '
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double precision :: h0i,hii,h00
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call i_H_j(det_i,det_i,N_int,h0i)
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print*,' < ref | H | det_i > = ',h0i
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print*,'computing the diagonal Hamiltonian matrix element of det_i '
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call i_H_j(ref_bitmask,det_i,N_int,hii)
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print*,'< det_i | H | det_i > = ',hii
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print*,'computing the first-order coefficient of det_i with H0=EN '
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double precision :: c_i
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call i_H_j(ref_bitmask,ref_bitmask,N_int,h00)
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c_i = h0i/(h00 - hii)
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print*,'c_i^{(1)} = ',c_i
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print*,''
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print*,'doing another single excitation on top of det_i'
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h1 = elec_alpha_num
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p1 = elec_alpha_num + 1
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s1 = 2
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call do_single_excitation(det_i,h1,p1,s1,i_ok)
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print*,'h1,p1,s1,i_ok'
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print*, h1,p1,s1,i_ok
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call i_H_j(det_i,det_i,N_int,h0i)
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print*,' < ref | H | det_i > = ',h0i
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print*,'computing the diagonal Hamiltonian matrix element of det_i '
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call i_H_j(ref_bitmask,ref_bitmask,N_int,h00)
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c_i = h0i/(h00 - hii)
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print*,'c_i^{(1)} = ',c_i
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print*,''
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print*,'Finding the excitation degree between two arbitrary determinants '
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integer :: exc(0:2,2,2)
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double precision :: phase
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integer :: h2,p2,s2,degree
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call get_excitation_degree(ref_bitmask,det_i,degree,N_int)
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print*,'degree = ',degree
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print*,'Finding the differences in terms of holes and particles, together with the fermionic phase '
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call get_excitation(ref_bitmask,det_i,exc,degree,phase,N_int)
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print*,'Fermionic phase for the excitation from ref_bitmask to det_i'
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print*,phase
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print*,'put the excitation information in a human readable format'
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call decode_exc(exc,degree,h1,p1,h2,p2,s1,s2)
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print*,'s1',s1
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print*,'h1,p1 = ',h1,p1
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print*,'s2',s2
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print*,'h2,p2 = ',h2,p2
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print*,''
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print*,'Finding the occupancy of det_i'
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integer, allocatable :: occ(:,:)
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integer :: n_occ_ab(2)
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allocate(occ(N_int*bit_kind_size,2))
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call bitstring_to_list_ab(det_i, occ, n_occ_ab, N_int)
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print*,'alpha electrons orbital occupancy'
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do i = 1, n_occ_ab(1) ! browsing the alpha electrons
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print*,occ(i,1)
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enddo
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print*,'beta electrons orbital occupancy'
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do i = 1, n_occ_ab(2) ! browsing the beta electrons
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print*,occ(i,2)
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enddo
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end
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subroutine example_determinants_psi_det
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use bitmasks ! you need to include the bitmasks_module.f90 features
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implicit none
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BEGIN_DOC
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! subroutine that illustrates the main features available in determinants using the psi_det/psi_coef
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END_DOC
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read_wf = .True.
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touch read_wf
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! you force the wave function to be set to the one in the EZFIO directory
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call routine_example_psi_det
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end
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subroutine routine_example_psi_det
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use bitmasks ! you need to include the bitmasks_module.f90 features
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implicit none
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BEGIN_DOC
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! subroutine that illustrates the main features available in determinants using many determinants
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END_DOC
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integer :: i,j
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integer, allocatable :: degree_list(:)
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integer, allocatable :: idx(:)
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allocate(degree_list(N_det),idx(0:N_det))
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print*,'Number of determinants in the wave function'
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print*,'N_det = ',N_det
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print*,''
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print*,'Printing in a human readable format all Slater determinants '
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do i = 1, N_det
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call debug_det(psi_det(1,1,i),N_int)
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enddo
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print*,''
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print*,'Number of states computed '
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print*,'N_states = ',N_states
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print*,'Printing the coefficients for all states for all Slater determinants '
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do j = 1, N_states
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print*,'State = ',j
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do i = 1, N_det
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write(*,'(I9,X,F16.10)')i,psi_coef(i,j)
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enddo
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enddo
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print*,''
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print*,'Finding the connection through a two-electron operator in the wave function'
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print*,'You want to know the connections of the first determinant '
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! wave function determinant exc degree list
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call get_excitation_degree_vector( psi_det , psi_det(1,1,1),degree_list,N_int,N_det,idx)
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double precision :: hij
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double precision, allocatable :: i_H_psi(:)
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allocate(i_H_psi(N_states))
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i_H_psi = 0.d0
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print*,'Computing <psi_det(1) | H | psi_det > = \sum_I c_I <psi_det(1)| H | psi_det(I)>'
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do i = 1, idx(0) ! number of Slater determinants connected to the first one
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print*,'Determinant connected'
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call debug_det(psi_det(1,1,idx(i)),N_int)
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print*,'excitation degree = ',degree_list(i)
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call i_H_j(psi_det(1,1,1) , psi_det(1,1,idx(i)),N_int,hij)
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do j = 1, N_states
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i_H_psi(j) += hij * psi_coef(idx(i),j)
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enddo
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enddo
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print*,'i_H_psi = ',i_H_psi
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end
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