The crystal structure of rubidium-VI near 50 GPa

The crystal structure of the high-pressure phase rubidium-VI (Rb-VI) has be en investigated near 50 GPa using monochromatic synchrotron X-ray diffracti on. Full profile refinements of powder diffraction data resulted in a solut ion with space group Cmca and 16 atoms in the orthorhombic unit cell. The p hase Rb-VI is isostructural to the recently determined oC16 structures of t he high-pressure phases Cs-V and Si-VI. Similar to the case of cesium, the oC16 structure of Rb appears at a pressure, where the electronic s --> d tr ansition is thought to be essentially completed. (C) 1999 Elsevier Science Ltd. All rights reserved.