Two interacting particles in a spherical pore J. Chem. Phys. 134, 064508 (2011) Thermodynamical approach to sympathetic cooling of neutral particles J. Chem. Phys. 134, 044109 (2011) We investigate the thermodynamic and dynamic properties of a three dimensional associating lattice gas ͑ALG͒ model through Monte Carlo simulations. The ALG model combines a soft core potential and orientational degrees of freedom. The competition of directional attractive forces and the soft core potential results in two coexisting liquid phases which are also connected through order-disorder critical transitions. The model presents structural order, density, and diffusion anomalies. Our study suggests that the dynamic fragile-to-strong transitions are associated to changes in structural order.

Monte Carlo simulation strategies for computing the wetting properties of fluids at geometrically rough surfaces J. Chem. Phys. 135, 184702 (2011) Semi-bottom-up coarse graining of water based on microscopic simulations J. Chem. Phys. 135, 184101 (2011) Hydrophobic interactions in presence of osmolytes urea and trimethylamine-N-oxide J. Chem. Phys. 135, 174501 (2011) Potential of mean force between identical charged nanoparticles immersed in a size-asymmetric monovalent electrolyte J. Chem. Phys. 135, 164705 (2011) Additional information on J. Chem. Phys. Using Monte Carlo simulations we investigate some new aspects of the phase diagram and the behavior of the diffusion coefficient in an associating lattice gas ͑ALG͒ model on different regions of the phase diagram. The ALG model combines a two dimensional lattice gas where particles interact through a soft core potential and orientational degrees of freedom. The competition between soft core potential and directional attractive forces results in a high density liquid phase, a low density liquid phase, and a gas phase. Besides anomalies in the behavior of the density with the temperature at constant pressure and of the diffusion coefficient with density at constant temperature are also found. The two liquid phases are separated by a coexistence line that ends in a bicritical point. The low density liquid phase is separated from the gas phase by a coexistence line that ends in tricritical point. The bicritical and tricritical points are linked by a critical -line. The high density liquid phase and the fluid phases are separated by a second critical -line. We then investigate how the diffusion coefficient behaves on different regions of the chemical potential-temperature phase diagram. We find that diffusivity undergoes two types of dynamic transitions: a fragile-to-strong transition when the critical -line is crossed by decreasing the temperature at a constant chemical potential; and a strong-to-strong transition when the critical -line is crossed by decreasing the temperature at a constant chemical potential.

We investigate the relation between thermodynamic and dynamic properties of an associating lattice gas (ALG) model. The ALG combines a three dimensional lattice gas with particles interacting through a soft core potential and orientational degrees of freedom. From the competition between the directional attractive forces and the soft core potential results two liquid phases, double criticality and density anomaly. We study the mobility of the molecules in this model by calculating the diffusion constant at a constant temperature, D. We show that D has a maximum at a density ρ max and a minimum at a density ρ min < ρ max . Between these densities the diffusivity differs from the one expected for normal liquids. We also show that in the pressure-temperature phase-diagram the line of extrema in diffusivity is close to the liquid-liquid critical point and it is partially inside the temperature of maximum density (TMD) line.

Monte Carlo simulation strategies for computing the wetting properties of fluids at geometrically rough surfaces J. Chem. Phys. 135, 184702 (2011) Semi-bottom-up coarse graining of water based on microscopic simulations J. Chem. Phys. 135, 184101 (2011) Hydrophobic interactions in presence of osmolytes urea and trimethylamine-N-oxide J. Chem. Phys. 135, 174501 (2011) Potential of mean force between identical charged nanoparticles immersed in a size-asymmetric monovalent electrolyte J. Chem. Phys. 135, 164705 (2011) Additional information on J. Chem. Phys. The Bell-Lavis model for liquid water is investigated through numerical simulations. The lattice-gas model on a triangular lattice presents orientational states and is known to present a highly bonded low density phase and a loosely bonded high density phase. We show that the model liquid-liquid transition is continuous, in contradiction with mean-field results on the Husimi cactus and from the cluster variational method. We define an order parameter which allows interpretation of the transition as an order-disorder transition of the bond network. Our results indicate that the order-disorder transition is in the Ising universality class. Previous proposal of an Ehrenfest second order transition is discarded. A detailed investigation of anomalous properties has also been undertaken. The line of density maxima in the HDL phase is stabilized by fluctuations, absent in the mean-field solution.

A molecular dynamics investigation of the structural and dynamic properties of the ionic liquid 1-n-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide J. Chem. Phys. 135, 124507 (2011) Dynamics of thermal diffusion in a linear temperature field J. Appl. Phys. 110, 044908 (2011) Soret motion in non-ionic binary molecular mixtures J. Chem. Phys. 135, 054102 (2011) On the coupling between slow diffusion transport and barrier crossing in nucleation J. Chem. Phys In this paper we investigate the dynamic properties of the minimal Bell-Lavis ͑BL͒ water model and their relation to the thermodynamic anomalies. The BL model is defined on a triangular lattice in which water molecules are represented by particles with three symmetric bonding arms interacting through van der Waals and hydrogen bonds. We have studied the model diffusivity in different regions of the phase diagram through Monte Carlo simulations. Our results show that the model displays a region of anomalous diffusion which lies inside the region of anomalous density, englobed by the line of temperatures of maximum density. Further, we have found that the diffusivity undergoes a dynamic transition which may be classified as fragile-to-strong transition at the critical line only at low pressures. At higher densities, no dynamic transition is seen on crossing the critical line. Thus evidence from this study is that relation of dynamic transitions to criticality may be discarded.

We investigate the relation between thermodynamic and dynamic properties of an associating lattice gas (ALG) model. The ALG combines a two dimensional lattice gas with particles interacting through a soft core potential and orientational degrees of freedom. From the competition between the directional attractive forces and the soft core potential results two liquid phases, double criticality and density anomaly. We study the mobility of the molecules in this model by calculating the diffusion constant at a constant temperature, D. We show that D has a maximum at a density ρ max and a minimum at a density ρ min < ρ max . Between these densities the diffusivity differs from the one expected for normal liquids. We also show that in the pressure-temperature phase-diagram the line of extrema in diffusivity is close to the liquid-liquid critical point and it is inside the temperature of maximum density (TMD) line. § To whom correspondence should be addressed (marcia.barbosa@ufrgs.br)

In this paper we investigate the solubility of a hard-sphere gas in a solvent modeled as an associating lattice gas. The solution phase diagram for solute at 5% is compared with the phase diagram of the original solute free model. Model properties are investigated both through Monte Carlo simulations and a cluster approximation. The model solubility is computed via simulations and is shown to exhibit a minimum as a function of temperature. The line of minimum solubility (TmS) coincides with the line of maximum density (TMD) for different solvent chemical potentials, in accordance with the literature on continuous realistic models and on the "cavity" picture.

We present a simple lattice model that consists of two competitive contact processes with local interactions on a one-dimensional lattice. The sites of the lattice can be empty or occupied by particles of type A or type B. The time evolution of the densities is governed by a master equation, whose transition among the states depends essentially on the spreading and annihilation rates of both particles. This is a competitive model where the stationary states are determined as a function of the spreading and annihilation rates. We employ mean-field approximations, at the level of one and two sites, and we obtain a phase diagram that shows four well distinguished phases, including a mixed one in which both particles coexist. Monte Carlo simulations show that this mixed phase no longer exists in the limit of large one-dimensional lattices. However, simulations of the model in two dimensions show that the mixed phase does not disappear as in the one-dimensional case. We also calculate some static critical exponents of the one-dimensional version of the model and we have shown that they belong to the directed percolation universality class.