Given a structure associated with a tensor, determines
        the rotation matrix for IEEE conversion according to
        the 1987 IEEE standards.

        Args:
            structure (Structure): a structure associated with the
                tensor to be converted to the IEEE standard
            refine_rotation (bool): whether to refine the rotation
                using SquareTensor.refine_rotation

def get_ieee_rotation(structure, refine_rotation=True):
        """
        Given a structure associated with a tensor, determines
        the rotation matrix for IEEE conversion according to
        the 1987 IEEE standards.

        Args:
            structure (Structure): a structure associated with the
                tensor to be converted to the IEEE standard
            refine_rotation (bool): whether to refine the rotation
                using SquareTensor.refine_rotation
        """
        # Check conventional setting:
        sga = SpacegroupAnalyzer(structure)
        dataset = sga.get_symmetry_dataset()
        trans_mat = dataset['transformation_matrix']
        conv_latt = Lattice(np.transpose(np.dot(np.transpose(
            structure.lattice.matrix), np.linalg.inv(trans_mat))))
        xtal_sys = sga.get_crystal_system()

        vecs = conv_latt.matrix
        lengths = np.array(conv_latt.abc)
        angles = np.array(conv_latt.angles)
        rotation = np.zeros((3, 3))

        # IEEE rules: a,b,c || x1,x2,x3
        if xtal_sys == "cubic":
            rotation = [vecs[i] / lengths[i] for i in range(3)]

        # IEEE rules: a=b in length; c,a || x3, x1
        elif xtal_sys == "tetragonal":
            rotation = np.array([vec / mag for (mag, vec) in
                                 sorted(zip(lengths, vecs),
                                        key=lambda x: x[0])])
            if abs(lengths[2] - lengths[1]) < abs(lengths[1] - lengths[0]):
                rotation[0], rotation[2] = rotation[2], rotation[0].copy()
            rotation[1] = get_uvec(np.cross(rotation[2], rotation[0]))

        # IEEE rules: c<a<b; c,a || x3,x1
        elif xtal_sys == "orthorhombic":
            rotation = [vec / mag for (mag, vec) in sorted(zip(lengths, vecs))]
            rotation = np.roll(rotation, 2, axis=0)

        # IEEE rules: c,a || x3,x1, c is threefold axis
        # Note this also includes rhombohedral crystal systems
        elif xtal_sys in ("trigonal", "hexagonal"):
            # find threefold axis:
            tf_index = np.argmin(abs(angles - 120.))
            non_tf_mask = np.logical_not(angles == angles[tf_index])
            rotation[2] = get_uvec(vecs[tf_index])
            rotation[0] = get_uvec(vecs[non_tf_mask][0])
            rotation[1] = get_uvec(np.cross(rotation[2], rotation[0]))

        # IEEE rules: b,c || x2,x3; alpha=beta=90, c<a
        elif xtal_sys == "monoclinic":
            # Find unique axis
            u_index = np.argmax(abs(angles - 90.))
            n_umask = np.logical_not(angles == angles[u_index])
            rotation[1] = get_uvec(vecs[u_index])
            # Shorter of remaining lattice vectors for c axis
            c = [vec / mag for (mag, vec) in
                 sorted(zip(lengths[n_umask], vecs[n_umask]))][0]
            rotation[2] = np.array(c)
            rotation[0] = np.cross(rotation[1], rotation[2])

        # IEEE rules: c || x3, x2 normal to ac plane
        elif xtal_sys == "triclinic":
            rotation = [vec / mag for (mag, vec) in sorted(zip(lengths, vecs))]
            rotation[1] = get_uvec(np.cross(rotation[2], rotation[0]))
            rotation[0] = np.cross(rotation[1], rotation[2])

        rotation = SquareTensor(rotation)
        if refine_rotation:
            rotation = rotation.refine_rotation()

        return rotation