SPINSGA

SPINSGA is a program package for evaluation of properties of spin-1/2 Heisenberg systems using the symmetric group approach. Nature of problem: This code computes different properties of spin-1/2 Heisenberg systems like ground state energies and wavefunctions and correlation functions. Solution method: The spin-1/2 Heisenberg matrix of a lattice is solved for the lowest eigenvalue and the corresponding eigenvector in a specific S, M-adapted spin basis. For this purpose a Davidson diagonalization procedure is employed. The product HC between the Hamiltonian matrix and the iteration vector is calculated in an implicit way, without ever setting up the H matrix. Once the eigenvector is found, several properties of the lattices can be calculated as expectation values. (Source: http://cpc.cs.qub.ac.uk/summaries/)