create_hamiltonian_old Function

    function create_hamiltonian_old(list_nI) result(hamil)
        ! try to also create the hamiltonian with the old implementation..
        ! although i think there needs to be more setup done..
        integer, intent(in) :: list_nI(:, :)
        HElement_t(dp) :: hamil(size(list_nI, 2), size(list_nI, 2))

        integer :: i, j

        t_lattice_model = .false.
        if (tGUGA) then
            call stop_all("create_hamiltonian_old", &
                          "modify get_helement for GUGA")
        end if
        do i = 1, size(list_nI, 2)
            do j = 1, size(list_nI, 2)
                hamil(i, j) = get_helement(list_nI(:, j), list_nI(:, i))
            end do
        end do
        t_lattice_model = .true.

    end function create_hamiltonian_old