Ba3AlO4H: Synthesis and structure of a new hydrogen-stabilized phase

摘要

The title compound and its deuteride were synthesized in high yield by sintering appropriate mixtures of BaH2(BaD2), BaO and Al2O3 in welded Ta containers at 1100 degrees C under a hydrogen (deuterium) pressure of 600-700 torr, The structure was determined by a combination of single crystal X-ray and time-of-flight powder neutron diffraction means (orthorhombic Pnma, Z = 4, a = 10.4911(9), b = 8.1518(7), c = 7.2399(6) Angstrom for the deuteride), The compound contains nominal Ba2+ cations, AlO45- complex anions and H-(D-) anions, The hydride is bound in a strongly distorted barium octahedron while the tetrahedral AlO45- anion is surrounded by eleven barium atoms in a peculiar polyhedral configuration. The HBa6 octahedra are linked together by corner-sharing to form a three dimension framework with large voids defined by eight of the HBa6 octahedra that are occupied by the tetrahedral AlO45- anions, The structure is closely related in a hierarchical way to that of orthorhombic inverse perovskitic Ba3GeO. (C) 1998 Academic Press. [References: 28]