Since the first term contains a restriction on the spin values whereas there is no restriction in the second term, the weighting factors (properly normalized) can be interpreted as probabilities of forming/not forming a link between the sites: P < n , m > l i n k = 1 − − e − − 2 β β J n m . The process can be easily adapted to antiferromagnetic spin systems, as it is sufficient to eliminate Z n , m s a m e in favor of Z n , m d i f f (as suggested by the change of sign in the interaction constant).