Core: fixed bug in Hamiltonian_Heisenberg_Pairs. The indices for pairs and quadruplets were wrong, as the in-cell indices werent used.
Core: fixed bug in Hamiltonian_Heisenberg_Pairs.
The indices for pairs and quadruplets were wrong, as the in-cell indices werent used.

spirit-code/spirit,spirit-code/spirit,spirit-code/spirit,spirit-code/spirit,spirit-code/spirit,spirit-code/spirit