Isothermal compression and phase transition in beryllium to 28.3 GPa

In situ high-pressure X-ray diffraction data for polycrystalline beryllium to 28.3 GPA at ambient temperature show that beryllium is transformed from the HCP phase (I) into a slightly distorted HCP phase (II) at pressures between 8.6 and 14.5 GPa. The volume change for the transition is extremely small ( approximately 0.4%); the effect of pressure on the c/a ratio for both the Be(I) and Be(II) phases is also very small.