Abstract and subjects
We conducted in-situ high-pressure synchrotron x-ray experiments on beryllium metal at pressures up to 7.9 GPa and temperatures up to 1373 K. A complete pressure (P)-volume (V)-temperature (T) equation of state (EOS) is determined based on the experiment, which includes temperature derivatives of elastic bulk modulus (at both constant pressure and constant volume) and pressure dependence of thermal expansivity. From this EOS, we calculate thermal pressure, heat capacity at constant volume, and thermodynamic Gru uneisen parameter as a function of temperature. Above similar to 600 K, our results show notable deviation from theoretical predictions using the quasiharmonic and local-density approximations, indicating that the free energy calculations need to be further improved within the current scheme of approximations. (c) 2013 AIP Publishing LLC.