Conserving controversies of melting line of graphite and graphene

Investigation of melting line of graphite and liquid carbon has long history. However, up to now there are still numerous controversies in the field, for instance, the melting temperatures obtained in different experiments are in very bad agrement. In the present paper we compare several models of carbon widely used in computational studies and the results of ab-initio simulations of liquid carbon. We show that the empirical models fail to reproduce the properties of liquid carbon correctly. We also discuss the "melting" of graphene

Water-like Anomalies of Core-Softened Fluids: Dependence on the Trajectories in (PρTP\rho T) Space

In the present article we carry out a molecular dynamics study of the core-softened system and show that the existence of the water-like anomalies in this system depends on the trajectory in $P-\rho-T$ space along which the behavior of the system is studied. For example, diffusion and structural anomalies are visible along isotherms, but disappears along the isochores and isobars, while density anomaly exists along isochors. We analyze the applicability of the Rosenfeld entropy scaling relations to this system in the regions with the water-like anomalies. It is shown that the validity of the of Rosenfeld scaling relation for the diffusion coefficient also depends on the trajectory in the $P-\rho-T$ space along which the kinetic coefficients and the excess entropy are calculated.Comment: 10 pages, 10 Fig

Quasicrystal vs Glass Transition: comparison structural and dynamical properties

Quasicrystals are solid structures with symmetry forbidden by crystallographic rules. Because of this some structural characteristics of quasicrystals, for instance, radial distribution function, can look similar to the ones of amorphous phases. This is of principal importance since radial distribution function is the main property to characterize the structure in molecular simulation. In the present paper we compare the radial distribution functions and dynamical properties of three systems in the vicinity of glass transition, quasicrystal formation and crystallization. We show that in spite of similarity of radial distribution functions the dynamical properties of a system in the vicinity of quasicrystal are qualitatively equivalent to the ones of crystal. Because of this combination the radial distribution functions with investigation of dynamics of the liquid allows unambiguously distinguish glass and quasicrystal

Dispersion of acoustic excitations in tetrahedral liquids

Investigation of the longitudinal and transverse excitations in liquids is of great importance for understanding the fundamentals of the liquid state of matter. One of the important questions is the temperature and density dependence of the frequency of the excitations. In our recent works it was shown that while in simple liquids the frequency of longitudinal excitations increases when the temperature is increased isochorically, in water the frequency can anomalously decrease with the temperature increase. In the present manuscript we study the dispersion curves of longitudinal and transverse excitations of water and liquid silicon modelled by Stillinger-Weber potential. We show that both substances demonstrate the anomaly of the dispersion curves, but it the case of water it is more pronounced

Phase diagram of a two-dimensional system which stabilizes Kagome lattice

Phase diagram of a two-dimensional system with a potential which stabilizes Kagome lattice is calculated. It is shown that this system demonstrate a set of crystalline and the regions of stability of these phases are calculated. The scenarios of melting of triangular and square crystals of the system are determined

Melting line and thermodynamic properties of a supeionic compound SrCl2_2 by molecular dynamics simulation

In the present paper we study the thermodynamic properties of superionic conductor $SrCl_2$ at high temperatures by means of molecular dynamics method. Firstly, we calculate the melting line. Then we compute the equations of state and the response functions (heat capacity, thermal expansion coefficient, etc) at the temperatures up to the melting. We show that the response functions show maxima or minima at the temperatures well above the temperature of transition into the conductive state, and therefore are not related to this transition

Possible phase transition in liquid Cesium at ambient pressure

We report a molecular dynamics study of liquid cesium at ambient pressure intended to check the possibility of liquid-liquid phase transformation at $T=590$ K. We find the presence of small kinks on thermodynamic characteristics of the system, but no phase transition

Properties of Liquid Iron along the Melting Line up to the Earth-core Pressures

We report a molecular dynamics study of transport coefficients and infinite frequency shear mod- ulus of liquid iron at high temperatures and high pressures. We observe a simultaneous rise of both shear viscosity and diffusion coefficient along the melting line and estimate if liquid iron can vitrify under Earth-core conditions. We show that in frames of the model studied in our work iron demonstrates a moderate increase of viscosity along the melting line. It is also demonstrated that in the limit of high temperatures and high pressures the liquid iron behaves similar to the soft spheres system with exponent n=4.6.Comment: 6 pages, 3 figure

Silica-Like Sequence of Anomalies in Core-Softened Systems

In this paper we present a simulation study of density, structural and diffusion anomalies in core-softened system introduced in our previous publications. It is well-known, that with appropriate parametrization, core-softened systems are remarkable model liquids that exhibit anomalous properties observed in tetrahedral liquids such as silica and water. It is widely believed that core-softened potentials demonstrate the water-like sequence of anomalies. We show that with increasing the depth of the attractive part of the potential the order of the region of anomalous diffusion and the regions of density and structural anomalies is inverted and have the silica-like sequence. We also show that the slope of the Widom line is negative like in water.Comment: 5 pages, 4 figures. arXiv admin note: text overlap with arXiv:1109.164

Water in Asbestos

We present the molecular simulation study of the behavior of water and sodium chloride solution confined in lizardite asbestos nanotube which is a typical example of hydrophilic confinement. The local structure, orientational and dynamic properties are studied. It is shown that the diffusion coefficient drops about two orders of magnitude comparing to the bulk case, and water in lizardite asbestos tubes experiences vitrification rather then crystallization upon cooling in accordance with the results for some other hydrophilic confinements. The behavior of sodium chloride solutions also considered and the formation of double layer is observed. It is shower that both sodium and chlorine have larger diffusion coefficients then water.Comment: 8 pages, 12 figure