from __future__ import print_function, division
import numpy as np
from sisl._help import _str
__all__ = ['Spin']
[docs]class Spin(object):
r""" Spin class to determine configurations and spin components.
The basic class `Spin` implements a generic method to determine a spin configuration.
Its usage can be summarized in these few examples:
>>> Spin(Spin.UNPOLARIZED) == Spin('unpolarized') == Spin()
True
>>> Spin(Spin.POLARIZED) == Spin('polarized') == Spin('p')
True
>>> Spin(Spin.NONCOLINEAR, dtype=np.complex128) == Spin('non-collinear') == Spin('nc')
True
>>> Spin(Spin.SPINORBIT, dtype=np.complex128) == Spin('spin-orbit') == Spin('so')
True
Note that a data-type may be associated with a spin-object. This is not to say
that the data-type is used in the configuration, but merely that it helps
any sub-classed or classes who use the spin-object to determine the
usage of the different spin-components.
Parameters
----------
kind : str or int, Spin, optional
specify the spin kind
dtype : numpy.dtype, optional
the data-type used for the spin-component.
"""
#: Constant for an un-polarized spin configuration
UNPOLARIZED = 0
#: Constant for a polarized spin configuration
POLARIZED = 1
#: Constant for a non-collinear spin configuration
NONCOLINEAR = 2
#: Constant for a spin-orbit spin configuration
SPINORBIT = 3
#: The :math:`\boldsymbol\sigma_x` Pauli matrix
X = np.array([[0, 1], [1, 0]], np.complex128)
#: The :math:`\boldsymbol\sigma_y` Pauli matrix
Y = np.array([[0, -1j], [1j, 0]], np.complex128)
#: The :math:`\boldsymbol\sigma_z` Pauli matrix
Z = np.array([[1, 0], [0, -1]], np.complex128)
__slots__ = ['_spins', '_kind', '_dtype']
def __init__(self, kind='', dtype=np.float64):
if isinstance(kind, Spin):
self._kind = kind._kind
self._dtype = kind._dtype
self._spins = kind._spins
return
# Copy data-type
self._dtype = dtype
if isinstance(kind, _str):
kind = kind.lower()
kind = {'unpolarized': Spin.UNPOLARIZED, '': Spin.UNPOLARIZED,
Spin.UNPOLARIZED: Spin.UNPOLARIZED,
'polarized': Spin.POLARIZED, 'p': Spin.POLARIZED,
Spin.POLARIZED: Spin.POLARIZED,
'non-colinear': Spin.NONCOLINEAR,
'non-collinear': Spin.NONCOLINEAR, 'nc': Spin.NONCOLINEAR,
Spin.NONCOLINEAR: Spin.NONCOLINEAR,
'spin-orbit': Spin.SPINORBIT, 'so': Spin.SPINORBIT,
Spin.SPINORBIT: Spin.SPINORBIT}.get(kind)
if kind is None:
raise ValueError(self.__class__.__name__ + ' initialization went wrong because of wrong '
'kind specification. Could not determine the kind of spin!')
# Now assert the checks
self._kind = kind
if np.dtype(dtype).kind == 'c':
spins = {self.UNPOLARIZED: 1,
self.POLARIZED: 2,
self.NONCOLINEAR: 4,
self.SPINORBIT: 4}.get(kind)
else:
spins = {self.UNPOLARIZED: 1,
self.POLARIZED: 2,
self.NONCOLINEAR: 4,
self.SPINORBIT: 8}.get(kind)
self._spins = spins
def __str__(self):
s = self.__class__.__name__
if self.is_unpolarized:
return s + '{{unpolarized, kind={}}}'.format(self.dkind)
if self.is_polarized:
return s + '{{polarized, kind={}}}'.format(self.dkind)
if self.is_noncolinear:
return s + '{{non-collinear, kind={}}}'.format(self.dkind)
return s + '{{spin-orbit, kind={}}}'.format(self.dkind)
[docs] def copy(self):
""" Create a copy of the spin-object """
return Spin(self.kind, self.dtype)
@property
def dtype(self):
""" Data-type of the spin configuration """
return self._dtype
@property
def dkind(self):
""" Data-type kind """
return np.dtype(self._dtype).kind
@property
def spins(self):
""" Number of spin-components """
return self._spins
@property
def kind(self):
""" A unique ID for the kind of spin configuration """
return self._kind
@property
def is_unpolarized(self):
""" True if the configuration is not polarized """
# Regardless of data-type
return self.kind == Spin.UNPOLARIZED
@property
def is_polarized(self):
""" True if the configuration is polarized """
return self.kind == Spin.POLARIZED
is_colinear = is_polarized
@property
def is_noncolinear(self):
""" True if the configuration non-collinear """
return self.kind == Spin.NONCOLINEAR
@property
def is_spinorbit(self):
""" True if the configuration is spin-orbit """
return self.kind == Spin.SPINORBIT
def __len__(self):
return self._spins
# Comparisons
def __lt__(self, other):
return self.kind < other.kind
def __le__(self, other):
return self.kind <= other.kind
def __eq__(self, other):
return self.kind == other.kind
def __ne__(self, other):
return not self == other
def __gt__(self, other):
return self.kind > other.kind
def __ge__(self, other):
return self.kind >= other.kind
def __getstate__(self):
return {
'spins': self.spins,
'kind': self.kind,
'dtype': self.dtype
}
def __setstate__(self, state):
self._spins = state['spins']
self._kind = state['kind']
self._dtype = state['dtype']