High-pressure powder X-ray diffraction study of Cu₅Si and pressure-driven isostructural phase transition

Abstract

The structural behaviour of Cu₅Si under high-pressure (HP) has been studied by angular dispersive X-ray diffraction up to 49.9 GPa. The experimental results suggest that a pressure-induced isostructural phase transition occurs around 13.5 GPa as revealed by a discontinuity in volume as a function of pressure. The lattice parameter decreases with the pressure increasing for both low-pressure (LP) and HP phases of Cu₅Si. However, a plot of the lattice parameter vs. pressure shows the existence of a plateau between 11.7 and 15.3 GPa. The bulk moduli, derived from the fitting of Birch–Murnaghan equation of state, are 150(2) GPa and 210(3) GPa for the LP phase and the HP phase of Cu₅Si, respectively. A change in the electronic state of the copper is assumed to govern the observed structural phase transition.

Keywords:

• intermetallic compounds
• crystal structure
• crystal symmetry
• phase transitions
• high-pressure studies
• X-ray diffraction
• Cu–Si

Acknowledgements

We acknowledge the National Synchrotron Light Source (NSLS) of Brookhaven National Laboratory (BNL) for provision of synchrotron radiation facilities beam line X17C. We are thankful for support from COMPRES (the Consortium for Materials Properties Research in Earth Sciences). This work was partly supported by the China Scholarship Council. We are grateful to the Editor and anonymous referees for their thorough reading of the manuscript and suggestions for improvement.