  The static and dynamic critical properties of the ferromagnetic q-state Potts
models on a square lattice with q = 2 and 3 are numerically studied via the
nonequilibrium relaxation method. The relaxation behavior of both the order
parameter and energy as well as that of the second moments are investigated,
from which static and dynamic critical exponents can be obtained. We find that
the static exponents thus obtained from the relaxation of the order parameter
and energy together with the second moments of the order parameter exhibit a
close agreement with the exact exponents, especially for the case of q = 2
(Ising) model, when care is taken in the choice of the initial states for the
relaxation of the second moments. As for the case of q = 3, the estimates for
the static exponents become less accurate but still exhibit reasonable
agreement with the exactly known static exponents. The dynamic critical
exponent for q = 2 (Ising) model is estimated from the relaxation of the second
moments of the order parameter with mixed initial conditions to give z(q = 2) =
2.1668(19).
