The short-time dynamic process for the two-dimensional Ising model with the nearest-neighbor coupling and the next-nearest-neighbor antiferromagnetic coupling in the critical domain is simulated by the Monte Carlo method. From the power law behavior of the initial order increase, the critical points and the initial dynamic exponent are determined.
The short-time dynamic process for the two-dimensional Ising model with the nearest-neighbor coupling and the next-nearest-neighbor antiferromagnetic coupling in the critical domain is simulated by the Monte Carlo method. From the power law behavior of the initial order increase, the critical points and the initial dynamic exponent are determined.
In this work the two-dimensional Ising model with nearest- and next-nearest-neighbor interactions is revisited. We obtain the dynamic critical exponents z and θ from short-time Monte Carlo simulations. The dynamic critical exponent z is obtained from the time behavior of the ratio [Formula: see text], whereas the non-universal exponent θ is estimated from the time correlation of the order parameter <M(0)M(t)> ~ tθ, where M(t) is the order parameter at instant t, d is the dimension of the system and <(⋯)> is the average of the quantity (⋯) over different samples. We also obtain the static critical exponents β and ν by investigating the time behavior of the magnetization.
With Monte Carlo simulations, we investigate short-time critical dynamics of the three-dimensional antiferromagnetic Ising model with a globally conserved magnetization m(s) (not the order parameter). From the power law behavior of the staggered magnetization (the order parameter), its second moment and the autocorrelation, we determine all static and dynamic critical exponents as well as the critical temperature. The universality class of m(s)=0 is the same as that without a conserved quantity, but the universality class of nonzero m(s) is different.
Comprehensive Monte Carlo simulations of the short-time dynamic behaviour are reported for the three-dimensional Ising model at criticality. Besides the exponent of the critical initial increase and the dynamic exponent z , the static critical exponents and as well as the critical temperature are determined from the power-law scaling behaviour of observables at the beginning of the time evolution. States of very high temperature as well as of zero temperature are used as initial states for the simulations.
Monte Carlo simulations of critical dynamics has been used to study the short-time process and scaling behavior of two-layer Ising model. The result shows that there are critical points even when the coupling between the two layers is not equal to zero; the short-time dynamic critical exponent θ was determined; the traditional critical exponent 1/νz was estimated also.Our result encouraged the supposition of the existence of the critical line and evidenced that this model was likely a weak universal model.
The critical relaxation from the low-temperature ordered state of the three-dimensional Ising model with competing interactions on a simple cubic lattice has been studied for the first time using the short-time dynamics method. Competition between exchange interactions is due to the ferromagnetic interaction between the nearest neighbors and the antiferromagnetic interaction between the next nearest neighbors. Particles containing 262144 spins with periodic boundary conditions have been studied. Calculations have been performed by the standard Metropolis Monte Carlo algorithm. The static critical exponents of the magnetization and correlation radius have been calculated. The dynamic critical exponent of the model under study has been calculated for the first time.
The short time dynamic behavior of the second-order phase transition in the two-dimensional fully frustrated XY model with nearest-neighbor (NN) and next-nearest-neighbor (NNN) couplings is investigated using Monte Carlo simulations. When x<1/2(x is the ratio between NNN and NN couplings), the transition temperature Tc and the dynamic and static critical exponents z, $2\ensuremath{\beta}/\ensuremath{\nu},$ and $\ensuremath{\nu}$ are estimated using the short-time dynamic scaling analysis. Except x close to the critical value 1/2, the critical exponents $2\ensuremath{\beta}/\ensuremath{\nu}$ and $\ensuremath{\nu}$ are found to be almost independent of the NNN coupling, indicating that the second-order phase transitions in the FFXY model, with or without NNN coupling, are in the same universality class. When x>1/2, the short-time dynamic study suggests that there is no second-order phase transition, in agreement with the previous result [Phys. Rev. B 62, R9287 (2000)].