X-ray diffraction and Raman studies of beryllium: Static and elastic properties at high pressures

We report combined x-ray and Raman studies of beryllium in helium and argon pressure media at pressures approaching 200 GPa. Our results are generally consistent with recent studies confirming the stability of the hexagonal close-packed phase to the highest pressures. However, the quasihydrostatic conditions of our studies lead to a stiffer equation of state (K₀=109.88, K₀^'=3.59) and a gradual approach toward a more ideal $c∕a$ ratio of 1.60 at 180 GPa. Combining our Raman and equation of state data, we are able to evaluate the pressure dependence of the elastic shear modulus (C₄₄=109.3, C₄₄^'=1.959). We discuss the comparison of our results with measurements using ultrasonic and dynamic techniques.