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[en] Application of the virial theorem to a Coulomb system of N particles neutralized by a continuous background, leads quite naturally to the definition of a 'virial' kinetic pressure for the system of particles, which is fundamentally positive, contrary to the thermodynamic one used in previous works, which has the drawback of giving negative values for sufficiently strong coupling
[fr]En appliquant le theoreme du viriel a un systeme coulombien de N particules neutralisees par un fond continu, on definit tres naturellement une pression cinetique 'virielle' du systeme de particules, qui est une quantite essentiellement positive, alors que la definition thermodynamique de la pression utilisee dans les travaux precedents a l'inconvenient de donner des valeurs negatives quand le parametre de couplage est suffisamment grand
[en] A new, wide-range equation of state (EOS) has been constructed for Be. The composite theoretical model incorporates ionization equilibrium and condensed-matter and multiphase physics. It also satisfies all thermodynamic equilibrium constraints. The theoretical EOS has been compared with all available high-pressure and high-temperature Be data, and satisfactory agreement is generally achieved. The most interesting feature is the theoretical prediction of melting at just below 220 GPa (2 Mb), indicating an extremely wide pressure range for solid Be. A striking feature is the appearance of shell-structure effects in physical-process paths: 2 large loops appear on the principal Hugoniot and the behavior of release isentropes from rho = rho0 is significantly affected
[en] Compression wave analysis started nearly 50 years ago with Fowles. Coperthwaite and Williams gave a method that helps identify simple and steady waves. We have been developing a method that gives describes the non-isentropic character of compression waves, in general. One result of that work is a simple analysis tool. Our method helps clearly identify when a compression wave is a simple wave, a steady wave (shock), and when the compression wave is in transition. This affects the analysis of compression wave experiments and the resulting extraction of the high-pressure equation of state.
[en] A new simple and accurate functional form for an attractive parameter α is introduced for Peng–Robinson equation of state. The modified Peng–Robinson equation of state is applied to calculate the density of different pure heavy hydrocarbons. The performance of this proposed equation of state for density calculations is examined with the corresponding experimental measurements and the results are compared with those obtained from the original Peng–Robinson equation of state. The new alpha function allows significant improvements of prediction of density. The overall average absolute deviation percentage of the calculated density of 12 heavy hydrocarbons obtained by this modified equation of state is 0.35%.
[en] Highlights: • Carnahan–Starling equations of state are simple and accurate. • Virial coefficients of lower orders can be represented by integer numbers. • Carnahan–Starling virial coefficients can give clue on the negativity issue. • Preciser virial coefficients do not guarantee a more accurate equation of state. - Abstract: Development of good equations of state for hard spheres is an important task in the study of real fluids. In a way consistent with other theoretical results, we generalize the famous Carnahan–Starling approach for arbitrary dimensions and apply it to four- and five-dimensional hard spheres. We obtain simple and integer representations for virial coefficients of lower orders and accurate equations of state. Since theoretically and practically validated, these results improve understanding of hard sphere fluids.