trans_corr_fac Function

    function trans_corr_fac(ilutI, src, tgt) result(weight)
        integer(n_int), intent(in) :: ilutI(0:NIfTot)
        integer, intent(in) :: src, tgt
        real(dp) :: weight
#ifdef DEBUG_
        character(*), parameter :: this_routine = "trans_corr_fac"
#endif
        real(dp) :: ni_opp, nj_opp

        ! if the spins are not the same, something went wrong..
        ASSERT(is_beta(src) .eqv. is_beta(tgt))

        ni_opp = 0.0_dp
        nj_opp = 0.0_dp

        if (is_beta(src)) then
            ! check if alpha orbital (i) and (j) in ilutI is occupied
            if (IsOcc(ilutI, get_alpha(src))) then
                nj_opp = 1.0_dp
            end if
            if (IsOcc(ilutI, get_alpha(tgt))) ni_opp = 1.0_dp
        else
            if (IsOcc(ilutI, get_beta(src))) nj_opp = 1.0_dp
            if (IsOcc(ilutI, get_beta(tgt))) ni_opp = 1.0_dp
        end if

        weight = exp(trans_corr_param * (nj_opp - ni_opp))

    end function trans_corr_fac