calc_eigenvalues_cmplx Function

    function calc_eigenvalues_cmplx(matrix) result(e_values)
        complex(dp), intent(in) :: matrix(:,:)
        real(dp) :: e_values(size(matrix,1))
        character(*), parameter :: this_routine = 'calc_eigenvalues_cmplx'

        integer :: n, info
        complex(dp) :: work(3*size(matrix,1))
        complex(dp) :: tmp_matrix(size(matrix,1),size(matrix,2))
        real(dp), allocatable :: rwork(:)

        n = size(matrix,1)

        tmp_matrix = matrix
        allocate(rwork(max(1, 3*n - 2)))
        call zheev('N','N', n, tmp_matrix, n, e_values, work, 3*n, rwork, info)
        if (info /= 0) call stop_all(this_routine, 'Failed in BLAS call.')
        deallocate(rwork)
        call sort(e_values)

    end function calc_eigenvalues_cmplx