Techniques for structural studies of liquids and amorphous materials by neutron diffraction at high pressures and temperatures

Abstract

This paper describes new techniques which permit the study of liquids and amorphous materials using neutron diffraction at high pressures and high temperatures up to 6.5 GPa and 1000 K using the Paris–Edinburgh cell. The set-up is based on an internal heating system, and combines a novel encapsulation method and highly transparent sintered diamond anvils to maximise the signal from a sample of 60 mm³ volume. We describe in detail the experimental set-up, the operation conditions, and the procedure for absorption correction and background subtraction. The method is illustrated by recent data collected on D₂O water at 6.5 GPa and 672 K.

Keywords:

• Powder neutron diffraction
• High pressure
• High temperature
• Liquids
• Amorphous materials

Acknowledgements

We wish to thank Dr. H. Stone (Cambridge University) for much help and assistance related to the temperature measurement using NARR as well as Duncan Francis (ISIS) for help during the experiments at ISIS. We are grateful to A. Soper (ISIS) for his interest in our work and many helpful discussions, as well as to M. Lécu from Industria S.A., Le Plessis Trevise (France), for his collaboration in the development of the sample encapsulation by laser welding. This work was funded by a fellowship from the Swiss National Science Foundation (TS, grant nr. 81EZ-68588), a research grant from EPSRC (JSL, RJN), and is supported by CCLRC through access to beamtime and other resources. We wish to dedicate this article to the memory of Jean-Michel Besson who was the Ph.D. thesis supervisor of YLG.