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

DOI: 10.1103/PhysRevB.79.184101

Authors: Denis Machon (LPMCN, Université Lyon-I, France) , P. Toulemonde (LPMCN; Institut Néel, CNRS and Université) , Paul Mcmillan (University College London) , Monica Amboage (Diamond Light Source) , A. Muñoz (Universidad de La Laguna) , R. Rodríguez-hernández (Universidad de La Laguna) , A. San Miguel (LPMCN, Université Lyon-I)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Review B

State: Published (Approved)
Published: May 2009

Abstract: The type-I clathrate Rb 6.15 Si 46 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 [K 0 =293(3)?GPa and K ? 0 =5.4(3) ].

Subject Areas: Physics

Facility: ESRF