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 or argon pressure medium 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 quasi-hydrostatic conditions of our studies lead to a stiffer equation of state (K{sub 0} = 109.88, K'{sub 0} = 3.59) and a gradual approach toward a more ideal c/a ratio of 1.60 at 180 GPa. Combining our Raman and EOS data, we are able to evaluate the pressure dependence of the elastic shear modulus (C{sub 44} = 109.3, C'{sub 44} = 1.959). We discuss the comparison of our results with measurements using ultrasonic and dynamic techniques