Time-scale invariance of relaxation processes of density fluctuation in slow neutron scattering in liquid cesium

The realization of idea of time-scale invariance for relaxation processes in liquids has been performed by the memory functions formalism. The best agreement with experimental data for the dynamic structure factor $S(k,\omega)$ of liquid cesium near melting point in the range of wave vectors (0.4 \ang^{-1} \leq k \leq 2.55 \ang^{-1}) is found with the assumption of concurrence of relaxation scales for memory functions of third and fourth orders. Spatial dispersion of the four first points in spectrum of statistical parameter of non-Markovity $\epsilon_{i}(k,\omega)$ at $i=1,2,3,4$ has allowed to reveal the non-Markov nature of collective excitations in liquid cesium, connected with long-range memory effect.Comment: REVTEX +3 ps figure

Is there a one-to-one correspondence between interparticle interactions and physical properties of liquid?

In this study, we present the original method for reconstructing the potential of interparticle interaction from statistically averaged structural data, namely, the radial distribution function of particles in many-particle system. This method belongs to a family of machine learning methods and is implemented through the differential evolution algorithm. As demonstrated for the case of the Lennard-Jones liquid taken as an example, there is no one-to-one correspondence between structure and potential of interparticle interaction of a many-particle disordered system at a certain thermodynamic state. Namely, a whole family of the Mie potentials determined by two parameters $p_{ 1 }$ and $p_{ 2 }$ related to each other according to a certain rule can reproduce properly a unique structure of the Lennard-Jones liquid at a given thermodynamic state. It is noteworthy that this family of the potentials quite correctly reproduces for the Lennard-Jones liquid the transport properties (in particular, the self-diffusion coefficient) over a temperature range as well as the dynamic structure factor, which is one of the key characteristics of the collective dynamics of particles.Comment: 29 pages, 7 figure

Crystal nucleation and cluster-growth kinetics in a model glass under shear

Crystal nucleation and growth processes induced by an externally applied shear strain in a model metallic glass are studied by means of nonequilibrium molecular dynamics simulations, in a range of temperatures. We observe that the nucleation-growth process takes place after a transient, induction regime. The critical cluster size and the lag-time associated with this induction period are determined from a mean first-passage time analysis. The laws that describe the cluster growth process are studied as a function of temperature and strain rate. A theoretical model for crystallization kinetics that includes the time dependence for nucleation and cluster growth is developed within the framework of the Kolmogorov-Johnson-Mehl-Avrami scenario and is compared with the molecular dynamics data. Scalings for the cluster growth laws and for the crystallization kinetics are also proposed and tested. The observed nucleation rates are found to display a nonmonotonic strain rate dependency

Dynamic Structure Factor in Liquid Cesium on the Basis of Time-Scale Invariance of Relaxation Processes

The dynamic structure factor S(k, ω) in liquid cesium near the melting point at T = 308 K is studied by means of Zwanzig-Mori's memory function formalism. The spectra of S(k, ω) are calculated on the basis of the idea of time-scale invariance of relaxation processes in liquid metals, which appear on the fourth relaxation level. The spectra of S(k, ω) obtained are compared with the results of an inelastic neutron scattering measurement. For the description of memory effects we use the statistical presentation of the non-Markovity parameter ε1(k, ω). We find that collective excitations at low wave-vector values have a non-Markovian nature. © 2002 MAIK "Nauka/Interperiodica"

Time-scale invariance of relaxation processes of density fluctuation in slow neutron scattering in liquid cesium

The idea of invariance is considered for an explanation of a specific nature of high-frequency collective excitations in liquid cesium. In particular, the idea of time-scale invariance of relaxation processes in liquids is suggested. This invariance can be easily taken into account by the memory functions formalism