Search

The action of an ultrashort laser pulse on a thin gold film was studied using a single-speed nonequilibrium combined continuum-atomistic model, which was further developed in the work. Three ablation modes were studied: supercritical expansion, phase explosion and mechanical spallation. The simulation results are compared with experimental data. The dependence of the amount of removed substance on the fluence of laser radiation was obtained. [ABSTRACT FROM AUTHOR]

The mechanism of homo-heterogeneous melting of aluminum with subsequent fragmentation of the melt under the influence of an ultrashort laser pulse is implemented within the framework of a nonequilibrium continuum model with dynamically adapting computational grids. The interaction of slow heterogeneous and fast homogeneous melting is investigated. Melt parameters and features of mechanical fragmentation of the liquid phase of the metal due to negative pressure developing in the hydrodynamic unloading wave are determined. [ABSTRACT FROM AUTHOR]

The article presents the results of atomistic modeling of the equilibrium thermophysical properties of gold in a wide temperature range (T~ 0.3-3.50 kK), covering the regions of first-order phase transitions of melting and evaporation. The temperature dependences of the density, linear size of the sample, coefficient of linear expansion, enthalpy, and heat capacity are determined. The obtained dependences of the properties of gold are approximated by polynomials of low degrees. There is an acceptable agreement between the obtained characteristics of gold and the experimental data. Numerical and graphic information on the obtained properties and results of comparison with experimental data is presented. [ABSTRACT FROM AUTHOR]

By constructing the thermal hysteresis of the enthalpy and density of the noble metals of gold (Au) and copper (Cu), non-equilibrium processes are investigated during the melting - crystallization phase transformations, i.e. during the solid-liquid transition. Thermal hysteresis is obtained from the atomistic modeling. The limiting temperatures of superheating of the solid phase during melting and undercooling of the liquid phase during crystallization of gold and copper are obtained. The possibility of the formation of highly superheatedundercooled metastable states of solid and liquid phases with rapid heating-cooling of the studied metals has been confirmed. The results obtained are compared with the results of alternative calculations. [ABSTRACT FROM AUTHOR]

Copper is a noble metal and has unique properties, due to which it is widely used in scientific research, industrial production and, more recently, in the problems of biomedicine. Using the molecular dynamics method, a series of calculations was performed to determine the lattice thermophysical properties of copper in a wide temperature range of 300K ≤ T ≤ 5800K. In the calculations, special attention is paid to the melting-crystallization and near-critical regions, in which cardinal changes in the thermophysical properties of the substance occur. The temperature dependences of the specific heat Cp(T), thermal conductivity κ(T), and density ρ(T) were among the studied characteristics of the phonon subsystem of Cu. Molecular - dynamic modeling was carried out using the potential of the embedded atom method (EAM). A comparison of the results with the results of experiments and alternative calculations showed a good agreement. The obtained calculation results were approximated by polynomials of low degrees.. [ABSTRACT FROM AUTHOR]

Of all the metals, gold is the most well-known and widely used material in scientific research, industrial production and, more recently, in biomedicine problems. In the temperature range 300 ≤ T ≤ 2000 K, including the region of the melting - crystallization phase transition, the results of modeling the phonon thermal conductivity of gold are presented. Phonon thermal conductivity plays an important role in modeling the mechanisms of interaction of pulsed laser radiation with gold in the framework of the two-temperature continuum model. In the region of the phase transition, overheating-undercooling of the solid phase occurs, the substance changes its structure. These phenomena are associated with changes in the phonon subsystem of gold, therefore, for mathematical modeling of heatingcooling, it is necessary to know the characteristic of heat transfer as the thermal conductivity of the phonon subsystem of gold. Obtaining the temperature dependence of phonon thermal conductivity in such a wide temperature range from experiment is problematic. In this work, phonon thermal conductivity was obtained by the direct non-equilibrium method in the framework of molecular dynamics modeling using the EAM potential. [ABSTRACT FROM AUTHOR]

A liquid - vapor coexistence curve was obtained for copper by the method of molecular dynamics modeling (MDM), and the corresponding critical parameters were determined: temperature, density, and pressure. The interaction potential of particles was of the "embedded atom" type (EAM). The critical temperature Tcr was determined from the MDM results using the average cluster size method in the critical region. To clarify the critical density value, the empirical rule of rectilinear diameter was used. The results of modeling of this work were compared with the results of evaluating of the critical parameters of copper by other authors using different approaches. [ABSTRACT FROM AUTHOR]

The article is dedicated to the 100th anniversary of the outstanding Soviet and Russian scientist, Academician of the USSR Academy of Sciences and the Russian Academy of Sciences Alexander Andreevich Samarskii, the founder of the Soviet and Russian school of mathematical modeling, the creator of the fundamental general theory of difference schemes, an outstanding teacher who brought up more than one generation of famous scientists, an active organizer and a bright advocate of science. Scientific activities of academician A.A. Samarskii is strongly associated with the Keldysh Institute of Applied Mathematics of Academy of Sciences of the USSR and the Russian Academy of Sciences and the Institute of Mathematical Modeling of the Russian Academy of Sciences, which he headed. A brilliant scientist and an excellent organizer, he laid down the potential to keep the world level of Russian science in the most important area of mathematical modeling for our country. [ABSTRACT FROM AUTHOR]