Article abstract
Nature Materials 6, 698 - 702 (2007)
Published online: 29 July 2007 | doi:10.1038/nmat1966
Subject Category: Geomaterials
Six-fold-coordinated phosphorus by oxygen in AlPO4 quartz homeotype under high pressure
Julio Pellicer-Porres1, Antonino Marco Saitta2, Alain Polian2, Jean Paul Itié3 & Michael Hanfland4
Abstract
AlPO4 belongs to the berlinite quartz homeotype family, which has been the subject of intense high-pressure research triggered by the supposed existence of reversible pressure-induced amorphization. X-ray diffraction experiments, complemented with ab initio calculations, demonstrate the existence of two high-pressure crystalline polymorphs and show that AlPO4 shares the same two-stage densification mechanism as silica. In the first step, a compact hexagonal sublattice of oxygen atoms is formed. In the second step, the cations redistribute in the interstices giving rise to a monoclinic distorted CaCl2 phase. The most outstanding feature of the phase is that phosphorous becomes six-fold coordinated by oxygen, adopting a configuration unknown so far in solid-state science. This finding opens possibilities in the high-pressure chemistry of phosphorus. The close relationship of AlPO4 with silica suggests the existence of completely unexplored families of compounds analogous to those of six-fold-coordinated silicates but based on PO6.
- ICMUV, Universidad de Valencia, c/Dr. Moliner 50, 46100 Burjassot, Valencia, Spain
- Physique des Milieux Denses, IMPMC, CNRS, Université Pierre et Marie Curie -Paris 6, 140 rue de Lourmel, 75015 Paris, France
- Synchrotron SOLEIL, L' Orme des Merisiers, Saint-Aubin, BP 48 91192 Gif-sur-Yvette Cedex, France
- E.S.R.F., BP 220, 38043 Grenoble Cedex, France
Correspondence to: Julio Pellicer-Porres1 e-mail: Julio.Pellicer@uv.es
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