magnopy.Energy.E_0

method

Energy.E_0(spin_directions, _normalize=True) → float

Computes classical energy of the spin Hamiltonian.

Parameters:

spin_directions(M, 3) array-like

Directions of spin vectors. Only directions of vectors are used, modulus is ignored. M is the amount of magnetic atoms in the Hamiltonian. The order of spin directions is the same as the order of magnetic atoms in spinham.magnetic_atoms.spins.

_normalizebool, default True

Whether to normalize the spin_directions or use the provided vectors as is. This parameter is technical and we do not recommend to use it at all.

Returns:

E_0float

Classic energy of state with spin_directions.

Examples

First, one need to create some spin Hamiltonian

>>> import numpy as np
>>> import magnopy
>>> cell = np.eye(3)
>>> atoms = dict(
... names = ["Fe"],
... spins = [1.5],
... g_factors = [2],
... positions = [[0, 0, 0]])
>>> convention = magnopy.Convention(
... multiple_counting=True,
... spin_normalized=False,
... c21=1,
... c22=-1)
>>> spinham = magnopy.SpinHamiltonian(
... cell=cell,
... atoms=atoms,
... convention=convention)

Then, add some parameters to the Hamiltonian

>>> spinham.add_21(alpha=0, parameter = np.diag([0, 0, -1]))
>>> spinham.add_22(
... alpha=0,
... beta=0,
... nu=(1,0,0),
... parameter = magnopy.converter22.from_iso(iso=1))

Now everything is ready to create an instance of the Energy class

>>> energy = magnopy.Energy(spinham)

Finally, energy an be used to compute classical energy of the Hamiltonian for arbitrary spin configuration.

>>> sd1 = [[1,0,0]]
>>> sd2 = [[0,1,0]]
>>> sd3 = [[0,0,1]]
>>> energy.E_0(sd1), energy.E_0(sd2), energy.E_0(sd3)
(-4.5, -4.5, -6.75)
>>> # The command above is equivalent to
>>> energy(sd1), energy(sd2), energy(sd3)
(-4.5, -4.5, -6.75)