(2, 1) terms

First type of the bilinear terms, in which both spin operators are associated with the same site.

\[\begin{split}C_{2,1} \sum_{\substack{\mu, \\ \alpha_1, \\ i_1, i_2}} J^{i_1, i_2}_{0; \alpha_1, \alpha_1} S_{\mu, \alpha_1}^{i_1} S_{\mu, \alpha_1}^{i_2}\end{split}\]

Relevant API

• magnopy.Convention.c21

  Convention constant.

• magnopy.SpinHamiltonian.add()

  Method to add the parameter to the Hamiltonian.

• magnopy.SpinHamiltonian.remove()

  Method to remove the parameter from the Hamiltonian.

• magnopy.SpinHamiltonian.p21

  An iterator over the parameters already added to the Hamiltonian.