A general algorithm for calculation of Heisenberg exchange integrals J in multispin systems

We propose a practical algorithm for calculating Heisenberg exchange integrals J in multispin systems using broken-symmetry methods. Because the Heisenberg J values are critical to the low-lying energy levels and the magnetic properties, this generalized spin-projection (GP) method will be important to evaluate the J values from density-functional theory (DFT) calculations.