title: Structural complexity in gallium under high pressure: relation to alkali elements.
abstract: Ga-II, the stable phase of Ga between 2 and 10 GPa at room temperature, is shown to have a complex 104-atom orthorhombic structure. A new phase, Ga-V, is found between 10 and 14 GPa, with a rhombohedral hR6 structure. Ga-II has a modulated layer structure like those recently reported for Rb-III and Cs-III, with similar 8- and 10-atom a-b layers stacked along the c axis in the sequence 8-10-8-8-10-8-8-10-8-8-10-8. The cI16 structure of Li and Na can be understood as a stacking of very similar 8-atom layers. It is suggested that a Hume-Rothery mechanism contributes to the occurrence of these complex structures in such different metals.
authors.affiliation: School of Physics and Centre for Science at Extreme Conditions, The University of Edinburgh, Mayfield Road, Edinburgh, EH9 3JZ, United Kingdom.
authors.forename: O
authors.initials: O
authors.lastname: Degtyareva
authors.forename: M I
authors.initials: MI
authors.lastname: McMahon
authors.forename: D R
authors.initials: DR
authors.lastname: Allan
authors.forename: R J
authors.initials: RJ
authors.lastname: Nelmes