Molecular-dynamics simulation of the high-pressure properties of rubidium

An embedded-atom potential for rubidium has been calculated with the parameters chosen with the use of the results of the static tests at a temperature of $300$ K and pressures up to $45$ GPa, as well as the results of the shock tests at pressures up to $39$ GPa. The molecular-dynamics simulation has been performed for temperatures of $300$—$10\,000$ K and pressures up to $\sim 94$ GPa. The potential determined from the shock-test data does not provide complete agreement with the static data for $300$ K. The pressure, energy, and specific heats $C_V$ and $C_p$ have been calculated for the compression up to $20$ $\%$ of the normal pressure and for temperatures up to $10\,000$ K. The derivative $(\partial p/\partial T)_V$ is positive for all of the molar-volume and temperature values except for a compression ratio of $30$ $\%$. Compression up to a factor of 2.5 or more is accompanied by the partial amorphization of the models, which is enhanced with heating. The calculations of the temperature along the Hugoniot curve under the assumption that the Grüneisen parameter and adiabatic compression modulus are independent of the temperature provide an incorrect molar-volume dependence of the pressure at $0$ K.