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High-pressure phase transformations, pressure-induced amorphization, and polyamorphic transition of the clathrate Rb6.15 Si46

MacHon, D; Toulemonde, P; San Miguel, A; McMillan, PF; Amboage, M; Muñoz, A; Rodríguez-Hernández, P; (2009) High-pressure phase transformations, pressure-induced amorphization, and polyamorphic transition of the clathrate Rb6.15 Si46. Physical Review B - Condensed Matter and Materials Physics , 79 (18) 10.1103/PhysRevB.79.184101.

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Abstract

The type-I clathrate Rb6.15 Si46 with partly empty cage sites has been studied up to 36 GPa using Raman spectroscopy, synchrotron x-ray diffraction in diamond-anvil cells, and ab initio total-energy and lattice-dynamics calculations. A first phase transition is observed at 13±1□GPa and a "volume collapse" transition within the clathrate structure is then observed at 24±1□GPa. Pressure-induced amorphization into a high-density amorphous (HDA) state occurs above P=33±1□GPa. The HDA form transforms into a low-density amorphous polymorph during decompression. During the compression study using angle dispersive synchrotron x-ray diffraction techniques we measured bulk modulus parameters for rocksalt-structured TaO, included adventitiously in the clathrate sample [K0 =293 (3) □GPa and K0′ =5.4 (3)]. © 2009 The American Physical Society.

Type:Article
Title:High-pressure phase transformations, pressure-induced amorphization, and polyamorphic transition of the clathrate Rb6.15 Si46
DOI:10.1103/PhysRevB.79.184101
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Chemistry

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