1,681 research outputs found
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 () 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 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 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 SrCl by molecular dynamics simulation
In the present paper we study the thermodynamic properties of superionic
conductor 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
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
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