title: Apparently complex high-pressure phase of gallium as a simple modulated structure.
abstract: The phase of gallium GaII, with symmetry C222(1) and 104 atoms per unit cell, has been recently reported as an example of structural complexity under high pressure. It is shown here that this phase is a simple modulated distortion of an average structure of Fddd symmetry with all atoms structurally equivalent. The modulation can be described with only 4 parameters and satisfies symmetry properties described by a centrosymmetric superspace group. The structural distortion is dominated by a frozen transversal mode associated with a single irreducible representation of Fddd, with a wave vector on the line Q, at an edge of the Brillouin zone. The average structure can be related with an hcp configuration through simple sliding of hcp layers, reminiscent of the hcp-bcc Bürgers mechanism.
authors.affiliation: Departamento de Física de la Materia Condensada, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Apdo 644, 48080 Bilbao, Spain.
authors.forename: J M
authors.initials: JM
authors.lastname: Perez-Mato
authors.forename: Luis
authors.initials: L
authors.lastname: Elcoro
authors.forename: Mois I
authors.initials: MI
authors.lastname: Aroyo
authors.forename: Hannelore
authors.initials: H
authors.lastname: Katzke
authors.forename: Pierre
authors.initials: P
authors.lastname: Tolédano
authors.forename: Zunbeltz
authors.initials: Z
authors.lastname: Izaola