arXiv subjects

R. E. Ryltsev

Publications and source records attributed to R. E. Ryltsev.

25 records · Page 2Linked to original sources

arXiv2015

Pade spectroscopy of structural correlation functions: application to liquid gallium

We propose the new method of fluid structure investigation which is based on numerical analytical continuation of structural correlation functions with Pade approximants. The method particularly allows extracting hidden structural features of non-ordered condensed matter systems from experimental diffraction data. The method has been applied to investigating the local order of liquid gallium which has non-trivial stricture in both the liquid and solid states. Processing the correlation functions obtained from molecular dynamic simulations, we show the method proposed reveals non-trivial structural features of liquid gallium such as the spectrum of length-scales and the existence of different types of local clusters in the liquid.

cond-mat.mtrl-sci↗

arXiv2015

Self-assembly of the decagonal quasicrystalline order in simple three-dimensional systems

For a three dimensional system we answer two questions, how simple a particle system might be to show the quasicrystal order and, what system features are the most important for quasicrystal formation? One-component system of particles with isotropic pair interaction is one of the simplest ones. We show that such system may be driven to three-dimensional decagonal (10-fold) quasicrystalline state just by purely repulsive, isotropic and monotonic interaction pair potential with two characteristic length scales; no attraction is needed. The second question we answer defining universal (nearly independent from the shape of the pair potential) effective integral parameters related to the first peak of the radial distribution function. The universality is illustrated by demonstrating the quasicrystalline order for a number of particle systems with absolutely different interaction potentials, both purely repulsive and attractive, but with the same effective integral parameters. Simple models like we study qualitatively describe effective interaction in molecular liquids, soft matter systems and metallic alloys for which quasicrystals have been experimentally observed.

cond-mat.soft↗

arXiv2015

Singularity band of velocity auto correlation function of Lennard-Jones fluid in complex $ω$-plain

It is well known from the quantum theory of strongly correlated systems that poles (or more subtle singularities) of dynamic correlation functions in complex plane usually correspond to the collective or localized modes. Here we address singularities of velocity autocorrelation function $Z$ in complex $ω$-plain for the one-component particle system with isotropic pair potential. We have found that naive few poles picture fails to describe analytical structure of $Z(ω)$ of Lennard-Jones particle system in complex plain. Instead of few isolated poles we see the singularity manifold of $Z(ω)$ forming branch cuts that suggests Lennard-Jones velocity autocorrelation function is a multiple-valued function of complex frequency. The brunch cuts are separated from the real axis by the well-defined "gap". The gap edges extend approximately parallel to the real frequency axis. The singularity structure is very stable under increase of the temperature; we have found its trace at temperatures even several orders of magnitude higher than the melting point. Our working hypothesis that the branch cut origin is related to the "interference" in $Z$ of one-particle kinetics and collective hydrodynamic motion.

cond-mat.soft↗

arXiv2015

Anomalous electrical conductivity in rapidly crystallized Cu${}_{50-x}$Zr${}_{x}$ (x = 50 - 66.6) alloys

Cu${}_{50-x}$Zr${}_{x}$ (x = 50, 54, 60 and 66.6) polycrystalline alloys were prepared by arc-melting. The crystal structure of the ingots has been examined by X-ray diffraction. Non-equilibrium martensitic phases with monoclinic structure were detected in all the alloys except Cu${}_{33.4}$Zr${}_{66.6}$. Temperature dependencies of electrical resistivity in the temperature range of T = 4 - 300 K have been measured as well as room temperature values of Hall coefficients and thermal conductivity. Electrical resistivity demonstrates anomalous behavior. At the temperatures lower than 20 K, their temperature dependencies are non-monotonous with pronounced minima. At elevated temperatures they have sufficiently non-linear character which cannot be described within framework of the standard Bloch--Grüneisen model. We propose generalized Bloch--Grüneisen model with variable Debye temperature which describes experimental resistivity dependencies with high accuracy. We found that both the electrical resistivity and the Hall coefficients reveal metallic-type conductivity in the Cu-Zr alloys. The estimated values of both the charge carrier mobility and the phonon contribution to thermal and electric conductivity indicate the strong lattice defects and structure disorder.

cond-mat.mtrl-sci↗

arXiv2014

Hydrodynamic anomalies in supercritical fluid

Using the molecular dynamics simulations we investigate properties of velocity autocorrelation function of Lennard-Jones fluid at long and intermediate time scales in wide ranges of temperature and density. We show that the amplitudes of the leading and subleading VAF time asymptotes, $a_1$ and $a_2$, show essentially non monotonous temperature and density dependence. There are two lines on temperature-density plain corresponding to maxima of $a_1$ ($a_2$) along isochors and isotherms situated in the supercritical fluid (hydrodynamic anomalies). These lines give insight into the stages of the fluid evolution into gas.

cond-mat.soft↗

arXiv2013

Two stage order-disorder transformation in simple monatomic supercritical fluid: superstable tetrahedral local order

The local order units of dense simple liquid are typically three dimensional (close packed) clusters: hcp, fcc and icosahedrons. We show that the fluid demonstrates the superstable tetrahedral local order up to temperatures several orders of magnitude higher than the melting temperature and down to critical density. While the solid-like local order (hcp, fcc) disappears in the fluid at much lower temperatures and far above critical density. We conclude that the supercritical fluid shows the temperature (density) driven two stage "melting" of the three dimensional local order. We also find that the structure relaxation times in the supercritical fluid are much larger than ones estimated for weakly interactive gas even far above the melting line.

cond-mat.dis-nn↗

arXiv2013

Superfragile glassy dynamics of onecomponent system with isotropic potential: competition of diffusion and frustration

We investigate glassy dynamical properties of one component three-dimensional system of particles interacting via pair repulsive potential by the molecular dynamic simulation in the wide region of densities. The glass state is superfragile and it has high glassforming ability. The glass transition temperature Tg has pronounced minimum at densities where the frustration is maximal.

cond-mat.soft↗