Papers by Keyword: Shock Hugoniot

Abstract: Response of materials to extreme temperature (T) and/or Pressure (P) conditions can be studied through, e.g., equations of states (EOS), which link between macroscopic observations to the microscopic consequences. Accurate knowledge of EOS is therefore always desirable, and plethora of different forms of EOS is proposed in literature. Of which, the most frequently used Mie-Grüneisen EOS coupled either with Debye-Model or Einstein-model within the quasiharmonic approximation requires prior knowledge of Grüneisen parameter (γ), characteristic temperature (θ) and their volume variation. At the pair-potential level, the Einstein characteristic temperature (θ_E) is derived through second-order potential derivatives. Although, many potential-energy-functional (PEF) are proposed for metallic systems, all including many-body effects, however, in order to compute θ_E effective pair-potential has to be deduced from PEF. But this procedure relies on some unavoidable approximations and fitting procedure. In this context, we have used energy-functional based definition of effective θ_E and for its volume dependence. We have employed tight-binding second-moment approximation (TB-SMA) to deduce cold energy curve to deduce θ_E and γ. Further, anharmonicity associated in bonding is parameterized; and it is shown that the parameter describing it is related to the thermodynamic Grüneisen parameter. Thus, the present scheme also circumvents additional empirical relation for γ (V). The present proposal is then employed to deduce equations of states and related thermo-physical properties; taking aluminum as a prototype. Results so generated to pressures more than 10 TPa and temperatures as high as 110 kK are compared and discussed in light of other simulated and experimental findings.

Abstract: We have studied the equation of states and vibrational properties of FeO using DFT based plane-wave pseudopotential (PW-DFT) within the generalized gradient approximation. The calculated cohesive properties at ambient condition, namely, lattice constant (a₀), bulk modulus (B₀) and its first pressure derivative (), are reported for B1-phase of FeO, in agreement with previous experimental and other theoretical results. A linear-response approach to the density functional theory was used to derive the phonon frequencies and phonon density of state (p-dos). Further, in order to calculate both static and dynamic equations of states, nearest-neighbour second-moment tight-binding energy model (TB-SMA) was used. Parameters of the present TB-SMA model were determined by the present ab initio pseudopotential calculations. It is found that the present simple TB-SMA scheme is able to mimic shock Hugoniot for such oxides correctly.

Abstract: Polymer materials have widespread applications in various situations for structural materials by themselves as well as by combining with other materials such as carbon fiber. Some of them are also candidates for energetic materials in space applications.[1] Due to their general use, shock response of them has attracted attention for many researchers.[2-4] One of the striking characteristics of the dynamic response of them is that stress and/or particle velocity profile has a relaxation structure of s range.[5, 6]

Abstract: Shock waves are indispensable tools for medical applications, and hence their interactions with human tissue become one of the most important basic research topics. In this paper, the determination of shock Hugoniot curves for liquids that can model human tissue, namely water, castor oil, and aqueous solutions of sodium chloride, sucrose and gelatin, at 10 and 20 weight percent are presented. Underwater shock waves were generated by ignition of 10 mg silver azide pellets and time variations of over-pressures were measured and simultaneously the shock speed was measured by the time of flight technique. Then shock Hugoniot curves were obtained, by assuming the Tait type equation of state, to relate the estimated density and measured pressure values. Results show in the cases of aqueous solutions that increasing amount of additives into water causes only a very minute decrease in the compressibility of the solution. This difference was more pronounced in the case of sodium chloride, less for gelatin, and almost none for sucrose aqueous solution.