Args:
            miller_index: viewing direction

        Returns:
            azim, elev for plotting

def _get_azimuth_elev(self, miller_index):
        """
        Args:
            miller_index: viewing direction

        Returns:
            azim, elev for plotting
        """
        if miller_index == (0, 0, 1) or miller_index == (0, 0, 0, 1):
            return 0, 90
        else:
            cart = self.lattice.get_cartesian_coords(miller_index)
            azim = get_angle([cart[0], cart[1], 0], (1, 0, 0))
            v = [cart[0], cart[1], 0]
            elev = get_angle(cart, v)
            return azim, elev