On the high-pressure phase transition in beryllium metal

The metal beryllium (Be) has been studied under high pressure using an electrical resistivity technique with in situ pressure calibration. A sluggish phase transition at 12 GPa is observed which the authors identify as the HCP to distorted HCP phase transition reported in a recent high-pressure X-ray diffraction study. However, a reanalysis of the X-ray data on the high-pressure phase Be(II) indicates that a smaller orthorhombic cell with four atoms fits the observed interplanar spacings. The observed intensity ratios of the diffraction lines can be explained reasonably well on the basis of the space group P2 1 2 1 2 with four Be atoms occupying 4c positions.