magnopy.SpinHamiltonian.purge#

method

SpinHamiltonian.purge(tolerance=None)[source]#

Removes parameters of the Hamiltonian that are smaller than the given tolerance.

Added in version 0.5.2.

Parameters:

tolerancefloat, default 1e-8 meV: Parameters with absolute value of all components smaller than the tolerance are removed. Expected to be non-negative. Expected to be in the same units as SpinHamiltonian.units. Default value is \(10^{-8}\) meV (converted to the units of the Hamiltonian).

Examples

First lets create a Hamiltonian

>>> import numpy as np
>>> import magnopy
>>> cell = np.eye(3)
>>> atoms = dict(
...     names=["Fe"], positions=[[0, 0, 0]], spins=[5 / 2], g_factors=[2]
... )
>>> convention = magnopy.Convention(
...     multiple_counting=True, spin_normalized=False, c22=1
... )
>>> spinham = magnopy.SpinHamiltonian(
...     cell=cell, atoms=atoms, convention=convention
... )

and add some parameters to it

>>> spinham.add(
...     nus=[(1, 0, 0)],
...     alphas=[0, 0],
...     parameter=np.eye(3) * 1e-9,
...     populate_equivalent=True,
... )
>>> spinham.add(
...     nus=[(0, 1, 0)],
...     alphas=[0, 0],
...     parameter=np.eye(3) * 1e-7,
...     populate_equivalent=True,
... )

There are four interaction parameters in the Hamiltonian

>>> len(spinham.parameters())
4
>>> for nus, alphas, parameter in spinham.parameters():
...     print(nus, alphas)
((-1, 0, 0),) (0, 0)
((0, -1, 0),) (0, 0)
((0, 1, 0),) (0, 0)
((1, 0, 0),) (0, 0)

Now if we purge the Hamiltonian with the default tolerance of 1e-8 meV, then only two parameters remain

>>> spinham.purge()
>>> len(spinham.parameters())
2
>>> for nus, alphas, parameter in spinham.parameters():
...     print(nus, alphas)
((0, -1, 0),) (0, 0)
((0, 1, 0),) (0, 0)