75 lines
2.1 KiB
Fortran
75 lines
2.1 KiB
Fortran
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BEGIN_PROVIDER [real*8, gradvec_old, (nMonoEx)]
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BEGIN_DOC
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! calculate the orbital gradient <Psi| H E_pq |Psi> by hand, i.e. for
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! each determinant I we determine the string E_pq |I> (alpha and beta
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! separately) and generate <Psi|H E_pq |I>
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! sum_I c_I <Psi|H E_pq |I> is then the pq component of the orbital
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! gradient
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! E_pq = a^+_pa_q + a^+_Pa_Q
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END_DOC
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implicit none
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integer :: ii,tt,aa,indx,ihole,ipart,istate
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real*8 :: res
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do indx=1,nMonoEx
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ihole=excit(1,indx)
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ipart=excit(2,indx)
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call calc_grad_elem(ihole,ipart,res)
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gradvec_old(indx)=res
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end do
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real*8 :: norm_grad
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norm_grad=0.d0
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do indx=1,nMonoEx
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norm_grad+=gradvec_old(indx)*gradvec_old(indx)
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end do
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norm_grad=sqrt(norm_grad)
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if (bavard) then
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write(6,*)
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write(6,*) ' Norm of the orbital gradient (via <0|EH|0>) : ', norm_grad
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write(6,*)
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endif
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END_PROVIDER
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subroutine calc_grad_elem(ihole,ipart,res)
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BEGIN_DOC
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! eq 18 of Siegbahn et al, Physica Scripta 1980
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! we calculate 2 <Psi| H E_pq | Psi>, q=hole, p=particle
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END_DOC
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implicit none
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integer :: ihole,ipart,mu,iii,ispin,ierr,nu,istate
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real*8 :: res
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integer(bit_kind), allocatable :: det_mu(:,:),det_mu_ex(:,:)
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real*8 :: i_H_psi_array(N_states),phase
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allocate(det_mu(N_int,2))
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allocate(det_mu_ex(N_int,2))
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res=0.D0
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do mu=1,n_det
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! get the string of the determinant
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call det_extract(det_mu,mu,N_int)
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do ispin=1,2
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! do the monoexcitation on it
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call det_copy(det_mu,det_mu_ex,N_int)
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call do_signed_mono_excitation(det_mu,det_mu_ex,nu &
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,ihole,ipart,ispin,phase,ierr)
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if (ierr.eq.1) then
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call i_H_psi(det_mu_ex,psi_det,psi_coef,N_int &
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,N_det,N_det,N_states,i_H_psi_array)
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do istate=1,N_states
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res+=i_H_psi_array(istate)*psi_coef(mu,istate)*phase
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end do
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end if
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end do
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end do
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! state-averaged gradient
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res*=2.D0/dble(N_states)
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end subroutine calc_grad_elem
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