This is a python program that evaluates the matrix elements of the Hamiltonian matrix of the quantum Heisenberg model for spin chains. Then the Hamiltonian matrix is diagonalized, and eigenvalues and eigenvectors are obtained. In the last step, the Total Position Spread tensor is computed.

It evaluates the matrix in open, and periodic boundary conditions.

You can compare the matrix built with this program looking at the results obtained here.

All results published used this software should cite the following:

• M. El Khatib, E. Fertitta, "Heisenberg: a program to the matrix calculation of the Heisenberg model in spin chains"