Bulletin of the American Physical Society
2005 14th APS Topical Conference on Shock Compression of Condensed Matter
Sunday–Friday, July 31–August 5 2005; Baltimore, MD
Session L6: Equation of State III |
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Chair: Damian Swift, Los Alamos National Laboratory Room: Hyatt Regency Chesapeake A/B |
Tuesday, August 2, 2005 3:30PM - 3:45PM |
L6.00001: Theoretical Equation of State for Beryllium-Oxide Jonathan Boettger, Kevin Honnell All-electron electronic structure calculations, using two distinct density functional approximations, have been used to predict the zero temperature equation of state and structural phase stability of beryllium-oxide (BeO) up to 1 TPa. A Sesame-type equation of state for BeO has been constructed using the new electronic structure results. The predicted 300 K isotherm and Hugoniot will be compared with experimental data. [Preview Abstract] |
Tuesday, August 2, 2005 3:45PM - 4:00PM |
L6.00002: Theoretical N$_{2}$ Hugoniot using MondoSCF density functional quantum energies and a very efficient Monte Carlo reweighting scheme M. Sam Shaw, C.J. Tymczak A Monte Carlo reweighting scheme is used to calculate the Hugoniot of molecular N$_{2}$ incorporating very accurate quantum energies. We first determine a reference potential fit to quantum calculations of the anisotropic pair interaction. Then the full many-body energy is evaluated for uncorrelated configurations from an NPT Monte Carlo reference simulation at pressure P$_{0}$ and temperature T$_{0}$. Each configuration is then reweighted to correspond to the distribution of the full energy at values of P and T chosen to maximize the overlap of the two distributions. Because the configurations are uncorrelated, only a few configurations are needed to give a statistically accurate EOS at P and T. The quantum energy calculations are computer intensive, but tractable due to the linear scaling of the MondoSCF density functional code. The PBE0 density functional is used with a 6-31g** basis set, shown to be convergent in the relevant energy differences. The resulting Hugoniot is in excellent agreement with Hugoniot data up to 40 GPa where N$_{2}$ remains molecular. [Preview Abstract] |
Tuesday, August 2, 2005 4:00PM - 4:30PM |
L6.00003: High Accuracy Equations of State: Status and Requirements for Theory Invited Speaker: I will discuss high accuracy equations of state in connection with two applications of current interest. The first is the development of accurate standards. Standards, whose off-Hugoniot EOS are known, are needed as pressure indicators in static compression experiments, and are useful for benchmarking new techniques, such as isentropic compression. Recent studies show inconsistencies among the shock-based standards that contribute significantly to the errors in static EOS measurements. The second area of interest are materials undergoing phase changes. High accuracy equilibrium EOS are needed in this case in order to infer non-equilibrium behavior from time-resolved shock data. I will discuss the accuracy requirements driven by these applications in terms of the static lattice and thermal contributions to the free energy. I will critically assess the status of ab initio methods with respect to these requirements. These considerations will be illustrated with recent work on the EOS of Au, Cu, Pt, Zr and Sn. [Preview Abstract] |
Tuesday, August 2, 2005 4:30PM - 4:45PM |
L6.00004: High Pressure {\&} High Temperature Equation of State and Magnetic Phase Transitions of Hematite from First Principles Sathya Hanagud, Xia Lu $\alpha -$Fe2O3 (Hematite) is of special interest in the design of multifunctional structural energetic materials (SEM), based on a thermite mixture of metal and metal oxide. In this paper, from first-principles, we obtained the thermodynamically complete EOS P = P($\rho $,T) for hematite for pressures up to 50GPa and temperatures up to 1000K. There are only a few theoretical works on hematite. The difficulty of techniques traces back to the complication of the description of highly correlated d-electrons induced localization of valence states in Fe, and the mixing of the O 2p states and the Fe 3d states. In this paper, we implemented the ground state calculations in the framework of DFT, using sGGA and projector augmented wave approach. Particularly, the Hubbard-U method is used to describe the on-site Coulomb interactions of strongly correlated d-electrons in Fe atoms. The lattice thermal contributions are obtained by populating the phonon modes, according to the Boltzmann statistics. In comparison to the previous studies, the thermal contributions to EOS from lattice vibrations are included. In addition, we investigate the magnetic phase transitions at pressures and temperatures of interest. In the applications of SEMs, pressures are lower than 50 GPa which exclude the HP phases. The phonon dispersion curves with Hubbard-U are compared with those without Hubbard-U. [Preview Abstract] |
Tuesday, August 2, 2005 4:45PM - 5:00PM |
L6.00005: Estimating the viscosity coefficient of liquid metals from Vibration-Transit theory Eric Chisolm, Duane Wallace We describe and test a simple method for calculating the viscosity coefficient $\eta$ for liquid metals over a range of densities and temperatures. The method uses a model of atomic motion in a liquid based on the Vibration-Transit (V-T) theory of liquid dynamics to calculate the self-diffusion coefficient $D$, and then uses $D$ and the Stokes-Einstein relation to compute $\eta$. We consider the accuracy of both the V-T model for $D$ and the Stokes-Einstein relation; we then compute $\eta$ for 21 liquid metals at melt at 1 bar, finding that our results agree with experiment to $18\%$ accuracy. This is somewhat more accurate than other empirical methods and not much less accurate than first priciples molecular dynamics calculations, while being substantially less computationally intensive than the latter. [Preview Abstract] |
Tuesday, August 2, 2005 5:00PM - 5:15PM |
L6.00006: Variation of Thermal Pressure along the Solid Hugoniot Hui Yu, Zizheng Gong, Xiufang Chen, Xudong Zhang, Fuqian Jing The behavior of thermal pressure P$_{TH}$ for all kinds of solid materials were investigated by using lattice dynamics theory and shock wave theory along the Hugoniot up to 500GPa. The results showed that for metals, ionic crystal and miners, etc., the ratio of the thermal pressure to the total pressure (P$_{TH}$ /P$_{Total})$ is approximately keeping in constant in a large pressure range not only for non-porous materials but also for porous materials at certain porosity. This confirms theoretically the existence of material constant parameter $\beta $ along solid Hugoniot (Gong \textit{et al}., Shock Compression of Condensed Matter-2003, edited by M. D. Furnish, Y. m. Gupta, and J. W. Forfes, pp.61-64.). Moreover, the volume dependence of the thermal pressure for all kinds of materials was addressed in our paper. [Preview Abstract] |
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