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Simulated tempering (ST) has attracted a great deal of attention in the last years, due to its capability to allow systems with complex dynamics to escape from regions separated by large entropic barriers. However its performance is strongly dependent on basic ingredients, such as the choice of the set of temperatures and their associated weights. Since the weight evaluations are not trivial tasks, an alternative approximated approach was proposed by Park and Pande (Phys. Rev. E 76, 016703 (2007)) to circumvent this difficulty. Here we present a detailed study about this procedure by comparing its performance with exact (free-energy) weights and other methods, its dependence on the total replica number R and on the temperature set. The ideas above are analyzed in four distinct lattice models presenting strong first-order phase transitions, hence constituting ideal examples in which the performance of algorithm is fundamental. In all cases, our results reveal that approximated weights work properly in the regime of larger R's. On the other hand, for sufficiently small R its performance is reduced and the systems do not cross properly the free-energy barriers. Finally, for estimating reliable temperature sets, we consider a simple protocol proposed at Comp. Phys. Comm. 128, 2046Comm. 128, (2014.

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In this work we discuss the behavior of the microcanonical temperature ∂S(E) ∂E obtained by means of numerical entropic sampling studies. It is observed that in almost all cases the slope of the logarithm of the density of states S(E) is not infinite in the ground state, since as expected it should be directly related to the inverse temperature 1 T . Here we show that these finite slopes are in fact due to finite-size effects and we propose an analytic expression a ln(bL) for the behavior of ∆S ∆E when L → ∞. To test this idea we use three distinct two-dimensional square lattice models presenting second-order phase transitions. We calculated by exact means the parameters a and b for the two-states Ising model and for the q = 3 and 4 states Potts model and compared with the results obtained by entropic sampling simulations. We found an excellent agreement between exact and numerical values. We argue that this new set of parameters a and b represents an interesting novel issue of investigation in entropic sampling studies for different models.

This work addresses the question on how the glass-forming ability (GFA) of a binary Pd-Ni metallic glass can be enhanced by the alloying effect of Pt. The structural features and slow dynamics of liquid and glassy states on both alloys are investigated by molecular dynamics simulations. Both alloys show typical features of glassy dynamics, namely, the non-Arrhenian behavior of diffusion and relaxation and the fractional Stokes-Einstein relation validity at low temperatures. On the basis of the analysis of the dynamical susceptibilities, we demonstrate that there is a strong influence of the alloying effect on the collective motion of the species, revealing that the GFA of the binary liquid increases with Pt alloying.

Low-dimensional systems of interacting particles demonstrate a variety of fascinating macroscopic properties. Experimentally investigated examples include two-dimensional electron systems in semiconductors structures and Abrikosov vortex lattices in superconductors; these systems share notable features in common, such as low-symmetry host crystal interactions. These interactions can be described in terms of a general statistical model: as systems driven by Coulombic forces and anisotropic bond energy. Through molecular-dynamics simulation we find that the expected hexagonal order disappears even for a weak tetragonal anisotropy, giving rise to a tetragonal structure with a finite-length ordering allowing for determination of the critical anisotropy parameter for the phase transition.