pymatgen.core.operations module

This module provides classes that operate on points or vectors in 3D space.

class MagSymmOp(affine_transformation_matrix, time_reversal, tol=0.01)

Bases: pymatgen.core.operations.SymmOp

Thin wrapper around SymmOp to extend it to support magnetic symmetry by including a time reversal operator. Magnetic symmetry is similar to conventional crystal symmetry, except symmetry is reduced by the addition of a time reversal operator which acts on an atom’s magnetic moment.

Initializes the MagSymmOp from a 4x4 affine transformation matrix and time reversal operator. In general, this constructor should not be used unless you are transferring rotations. Use the static constructors instead to generate a SymmOp from proper rotations and translation.

Parameters

• affine_transformation_matrix (4x4 array) – Representing an affine transformation.

• time_reversal (int) – 1 or -1

• tol (float) – Tolerance for determining if matrices are equal.

as_dict()

Returns

MSONABle dict

as_xyzt_string()

Returns a string of the form ‘x, y, z, +1’, ‘-x, -y, z, -1’, ‘-y+1/2, x+1/2, z+1/2, +1’, etc. Only works for integer rotation matrices

classmethod from_dict(d)

Parameters

d – dict

Returns

MagneticSymmOp from dict representation.

static from_rotation_and_translation_and_time_reversal(rotation_matrix=((1, 0, 0), (0, 1, 0), (0, 0, 1)), translation_vec=(0, 0, 0), time_reversal=1, tol=0.1)

Creates a symmetry operation from a rotation matrix, translation vector and time reversal operator.

Parameters

• rotation_matrix (3x3 array) – Rotation matrix.

• translation_vec (3x1 array) – Translation vector.

• time_reversal (int) – Time reversal operator, +1 or -1.

• tol (float) – Tolerance to determine if rotation matrix is valid.

Returns

MagSymmOp object

classmethod from_symmop(symmop, time_reversal)

Initialize a MagSymmOp from a SymmOp and time reversal operator.

Parameters

• symmop (SymmOp) – SymmOp

• time_reversal (int) – Time reversal operator, +1 or -1.

Returns

MagSymmOp object

static from_xyzt_string(xyzt_string)

Parameters

xyz_string – string of the form ‘x, y, z, +1’, ‘-x, -y, z, -1’, ‘-2y+1/2, 3x+1/2, z-y+1/2, +1’, etc.

Returns

MagSymmOp object

operate_magmom(magmom)

Apply time reversal operator on the magnetic moment. Note that magnetic moments transform as axial vectors, not polar vectors.

See ‘Symmetry and magnetic structures’, Rodríguez-Carvajal and Bourée for a good discussion. DOI: 10.1051/epjconf/20122200010

Parameters

• magmom – Magnetic moment as electronic_structure.core.Magmom

• or as list or np array-like (class) –

Returns

Magnetic moment after operator applied as Magmom class

class SymmOp(affine_transformation_matrix, tol=0.01)

Bases: monty.json.MSONable

A symmetry operation in cartesian space. Consists of a rotation plus a translation. Implementation is as an affine transformation matrix of rank 4 for efficiency. Read: http://en.wikipedia.org/wiki/Affine_transformation.

affine_matrix

A 4x4 numpy.array representing the symmetry operation.

Initializes the SymmOp from a 4x4 affine transformation matrix. In general, this constructor should not be used unless you are transferring rotations. Use the static constructors instead to generate a SymmOp from proper rotations and translation.

Parameters

• affine_transformation_matrix (4x4 array) – Representing an affine transformation.

• tol (float) – Tolerance for determining if matrices are equal.

apply_rotation_only(vector)

Vectors should only be operated by the rotation matrix and not the translation vector.

Parameters

vector (3x1 array) – A vector.

are_symmetrically_related(point_a, point_b, tol=0.001)

Checks if two points are symmetrically related.

Parameters

• point_a (3x1 array) – First point.

• point_b (3x1 array) – Second point.

• tol (float) – Absolute tolerance for checking distance.

Returns

True if self.operate(point_a) == point_b or vice versa.

as_dict()

Returns

MSONAble dict.

as_xyz_string()

Returns a string of the form ‘x, y, z’, ‘-x, -y, z’, ‘-y+1/2, x+1/2, z+1/2’, etc. Only works for integer rotation matrices

static from_axis_angle_and_translation(axis, angle, angle_in_radians=False, translation_vec=(0, 0, 0))

Generates a SymmOp for a rotation about a given axis plus translation.

Parameters

• axis – The axis of rotation in cartesian space. For example, [1, 0, 0]indicates rotation about x-axis.

• angle (float) – Angle of rotation.

• angle_in_radians (bool) – Set to True if angles are given in radians. Or else, units of degrees are assumed.

• translation_vec – A translation vector. Defaults to zero.

Returns

SymmOp for a rotation about given axis and translation.

classmethod from_dict(d)

Parameters

d – dict

Returns

SymmOp from dict representation.

static from_origin_axis_angle(origin, axis, angle, angle_in_radians=False)

Generates a SymmOp for a rotation about a given axis through an origin.

Parameters

• origin (3x1 array) – The origin which the axis passes through.

• axis (3x1 array) – The axis of rotation in cartesian space. For example, [1, 0, 0]indicates rotation about x-axis.

• angle (float) – Angle of rotation.

• angle_in_radians (bool) – Set to True if angles are given in radians. Or else, units of degrees are assumed.

Returns

SymmOp.

static from_rotation_and_translation(rotation_matrix=((1, 0, 0), (0, 1, 0), (0, 0, 1)), translation_vec=(0, 0, 0), tol=0.1)

Creates a symmetry operation from a rotation matrix and a translation vector.

Parameters

• rotation_matrix (3x3 array) – Rotation matrix.

• translation_vec (3x1 array) – Translation vector.

• tol (float) – Tolerance to determine if rotation matrix is valid.

Returns

SymmOp object

static from_xyz_string(xyz_string)

Parameters

xyz_string – string of the form ‘x, y, z’, ‘-x, -y, z’, ‘-2y+1/2, 3x+1/2, z-y+1/2’, etc.

Returns

SymmOp

property inverse

Returns inverse of transformation.

static inversion(origin=(0, 0, 0))

Inversion symmetry operation about axis.

Parameters

origin (3x1 array) – Origin of the inversion operation. Defaults to [0, 0, 0].

Returns

SymmOp representing an inversion operation about the origin.

operate(point)

Apply the operation on a point.

Parameters

point – Cartesian coordinate.

Returns

Coordinates of point after operation.

operate_multi(points)

Apply the operation on a list of points.

Parameters

points – List of Cartesian coordinates

Returns

Numpy array of coordinates after operation

static reflection(normal, origin=(0, 0, 0))

Returns reflection symmetry operation.

Parameters

• normal (3x1 array) – Vector of the normal to the plane of reflection.

• origin (3x1 array) – A point in which the mirror plane passes through.

Returns

SymmOp for the reflection about the plane

property rotation_matrix

A 3x3 numpy.array representing the rotation matrix.

static rotoreflection(axis, angle, origin=(0, 0, 0))

Returns a roto-reflection symmetry operation

Parameters

• axis (3x1 array) – Axis of rotation / mirror normal

• angle (float) – Angle in degrees

• origin (3x1 array) – Point left invariant by roto-reflection. Defaults to (0, 0, 0).

Returns

Roto-reflection operation

transform_tensor(tensor)

Applies rotation portion to a tensor. Note that tensor has to be in full form, not the Voigt form.

Parameters

tensor (numpy array) – a rank n tensor

Returns

Transformed tensor.

property translation_vector

A rank 1 numpy.array of dim 3 representing the translation vector.