Volume 86, Number 5, June 2009
Article Number 56001
Number of page(s) 5
Section Condensed Matter: Structural, Mechanical and Thermal Properties
Published online 09 June 2009
EPL, 86 (2009) 56001
DOI: 10.1209/0295-5075/86/56001

Instability of CaLi2 at high pressure: Theoretical prediction and experimental results

J. S. Tse1, D. D. Klug2, S. Desgreniers3, J. S. Smith3 and R. Dutrisac2

1   Department of Physics and Engineering Physics, University of Saskatchewan - Saskatoon, Saskatchewan, Canada S7N 5E2
2   Steacie Institute for Molecular Sciences, National Research Council of Canada - Ottawa, Ontario, Canada K1A 0R6
3   Laboratoire de physique des solides denses, Department of Physics, University of Ottawa - Ottawa, Ontario, Canada K1N 6N5

received 17 April 2009; accepted in final form 7 May 2009; published June 2009
published online 9 June 2009

Hexagonal CaLi2 has been predicted to undergo a bifurcated lattice distortion into polymorphs that may be candidates for superconductivity at high pressure. In this study, density functional and experimental X-ray diffraction techniques are employed to investigate the high-pressure stability of hexagonal CaLi2. Calculated enthalpies of hexagonal CaLi2 and elemental Ca and Li indicate that CaLi2 becomes unstable against segregation at pressures above 7 GPa. Our predictions are corroborated by powder X-ray diffraction measurements which show that the application of non-hydrostatic pressure leads to a partial decomposition of CaLi2 to elemental species of Ca and Li. A quantitative phase analysis of hexagonal CaLi2 and cubic Ca clearly shows an increase of the latter for pressures above 14 GPa. Finally, it is suggested that the recently reported superconductivity of CaLi2 at high pressure may contain decomposed Ca and Li.

61.05.cp - X-ray diffraction.
71.20.Lp - Intermetallic compounds.

© EPLA 2009