Equations of state for sapphire, silica, periclase, and rutile have been developed, which are applicable in a wide range of pressures and densities. The results of a comparison with available data ...obtained at high pressures in shock-wave experiments for crystalline and porous samples are presented.
A review of modern lines of research in the field of ultrafast magnetoacoustics is presented. Effects of interaction of ultrashort (picosecond) acoustic pulses with a magnetic subsystem of magnetic ...films and particles, as well as interaction of surface acoustic waves excited by femtosecond laser pulses with magnetic nanostructures, are considered. A separate direction of modern ultrafast magnetoacoustics involves interaction of surface acoustic waves with a magnetic subsystem in planar nanostructures. The conditions of this interaction for nonuniform magnetization modes are unclear and effects of interaction of surface acoustic waves with metasurfaces have been poorly studied. A promising method of excitation and detection of surface magnetoelastic waves in metal films and planar nanostructures is to apply the “transient grating” technique, which makes it possible to use modern femtosecond lasers and has very good temporal resolution. The main results of experiments on excitation of magnetoelastic modes in films and planar periodic nanostructures upon ultrafast laser excitation are discussed and the models of magnetoelastic nonlinear dynamics obtained by researchers all over the world over the last decade have been analyzed.
The mechanism of the oxidative coupling of methane (OCM), a reaction discovered in the early 1980s, and the development of approaches to kinetic description of this reaction are analyzed. In addition ...to being of potential practical significance as a single-step synthetic route from methane to ethylene, a valuable chemical and petrochemical semiproduct, OCM was the first heterogeneous–homogeneous process of this hitherto unknown type. Its distinctive feature is that it is impossible to separately determine the methane conversion via the main pathway (into C
2
hydrocarbons) in the homogeneous phase and on the catalyst surface, because reactive intermediates (methyl radicals) result from the interaction of methane molecules with active sites of the surface, while the primary OCM product (ethane) results from the recombination of these radicals in the gas phase. The correlation between the phenomenological regularities of the OCM process and its mechanism, the correlation between the nature of the active sites and the mechanism of activation of methane and oxygen, and the possibility of constructing a self-consistent kinetic model taking into account the specific features of the process—redox nature of the active sites and the free-radical character of the major intermediate compounds—are analyzed in detail.
The subject of high-energy-density (HED) states in matter is of considerable importance to numerous branches of basic as well as applied physics. Intense heavy-ion beams are an excellent tool to ...create large samples of HED matter in the laboratory with fairly uniform physical conditions. Gesellschaft für Schwerionenforschung, Darmstadt, is a unique worldwide laboratory that has a heavy-ion synchrotron, SIS18, that delivers intense beams of energetic heavy ions. Construction of a much more powerful synchrotron, SIS100, at the future international facility for antiprotons and ion research (FAIR) at Darmstadt will lead to an increase in beam intensity by 3 orders of magnitude compared to what is currently available. The purpose of this Letter is to investigate with the help of two-dimensional numerical simulations, the potential of the FAIR to carry out research in the field of HED states in matter.
Results of theoretical calculations and experimental measurements of the equation of state (EOS) at extreme conditions are discussed and applied to aluminum. It is pointed out that the available high ...pressure and temperature information covers a broad range of the phase diagram, but only irregularly and, as a rule, is not thermodynamically complete; its generalization can be done only in the form of a thermodynamically complete EOS. A multi-phase EOS model is presented, accounting for solid, liquid, gas, and plasma states, as well as two-phase regions of melting and evaporation. The thermodynamic properties of aluminum and its phase diagram are calculated with the use of this model. Theoretical calculations of thermodynamic properties of the solid, liquid, and plasma phases, and of the critical point, are compared with results of static and dynamic experiments. The analysis deals with thermodynamic properties of solid aluminum at T = 0 and 298 K from different band-structure theories, static compression experiments in diamond anvil cells, and the information obtained in isentropic-compression and shock-wave experiments. Thermodynamic data in the liquid state, resulting from traditional thermophysical measurements, “exploding wire” experiments, and evaluations of the critical point are presented. Numerous shock-wave experiments for aluminum have been done to measure shock adiabats of crystal and porous samples, release isentropes, and sound speed in shocked metal. These data are analyzed in a self-consistent manner together with all other available data at high pressure. The model's results are shown for the principal shock adiabat, the high-pressure melting and evaporation regions and the critical point of aluminum. New experimental and theoretical data helped to improve the description of the high-pressure, high-temperature aluminum liquid. The present EOS describes with high accuracy and reliability the complete set of available information.
In a recent paper, detailed numerical simulations of a proposed experimental scheme named LAPLAS, which stands for Laboratory Planetary Sciences, were reported. These simulations showed that ...employing intense ion beams as a driver, one can implode samples of Fe to high energy density (HED) states that are predicted to exist in the interiors of the Earth and more massive extrasolar rocky planets, the super-Earths. The driver parameters were chosen to match those of the ion beam that will be available at the Future Facility for Antiprotons and Ion Research (FAIR) in a few years. This work has been thoroughly extended by carrying out more simulations while systematically varying the beam and the target parameters in order to examine the stability and the robustness of the LAPLAS scheme. The simulations suggest that the results are rather insensitive to significant variations in the beam and the target parameters, which is a very good sign for the success of the experiment. Moreover, two different equation of state (EOS) models, including a semi-empirical model and the SESAME EOS data, respectively, have been used for Fe. Good agreement has been found between the two sets of results.
The validity of using kinetic scheme reduction procedures to compare various kinetic models as well as the values of kinetic parameters of individual steps present in the literature is analyzed. The ...peculiarities of the development of the gas-phase reaction block as a part of the heterogeneous-homogeneous model of the oxidative coupling of methane (OCM) are considered and approaches to the selection of kinetic parameters of elementary steps are analyzed. It has been demonstrated that kinetic models developed in accordance with the principle of “independence of kinetic parameters” can exhibit low predictive power due to existing uncertainties in the values of the parameters presented in well-known review papers and databases. In addition, the effects of the accounting of the heterogeneous reaction block and variation of the OCM reaction conditions on the results of the reduction of the detailed kinetic scheme are addressed. It has been shown that the use of reduction procedures to analyze the mechanism of complex processes is limited due to the high degree of conjugation between their individual stages and the strong dependence of kinetic constants on the parameters of state.
An equation of state is a fundamental characteristic of a substance. It is necessary in numerous studies and practically important problems of high energy density physics. In this review, we consider ...the modern requirements to equations of state, theoretical and experimental methods used to study the thermodynamic properties of a substance, different aspects of constructing wide-range equations of state, and examples of application of wide-range equations of state in simulation of high-energy processes.
Measurements of the brightness temperature and compressibility of a dense silicon plasma formed by powerful shock waves (SWs) passing through a single‐crystal sample have been carried out. Plane SWs ...were created using an explosive technique: the traditional plane acceleration of a steel driver plate made it possible to obtain pressures in silicon up to 133 GPa, and the use of “Mach” cumulative generators realized the pressures up to 510 GPa. The shock Hugoniot of silicon was determined by the impedance matching with α‐quartz as the reference. The intensity of emitted thermal radiation was measured in the infrared range λ ∼ 1.5 μm, where silicon is optically transparent, and in the visible range of the spectrum. A significant (up to five times) understatement of the measured values of the brightness temperature in comparison with the values calculated by the equation of state was found. Taking into account the reflective properties of the SW in silicon does not lead to an agreement with the experiment. The estimates of relaxation processes behind the shock front suggest the presence of a zone of the establishment of ionization equilibrium with a width of ∼10 μm.
Results of theoretical calculations and experimental measurements of the equation of state (EOS) are discussed and applied to silver. The thermodynamic properties of silver and its phase diagram are ...calculated with the use of multi-phase EOS model. Theoretical calculations of thermodynamic properties of the solid, liquid, and plasma phases, and of the critical point, are compared with results of experiments. The analysis deals with thermodynamic properties of solid silver at T = 0 and 298 K from different band-structure theories, static compression experiments in diamond anvil cells, and the information obtained in shock-wave experiments. Thermodynamic data in the liquid and plasma states, resulting from traditional thermophysical measurements, "exploding wire" experiments, evaluations of the critical point and measurements of the principal Hugoniot are presented. These data are analyzed in a self-consistent manner.
PDF
