title: Pressure dependent incommensuration in Rb-IV.
abstract: Rb-IV is found to have an incommensurate composite structure, comprising a tetragonal host framework and a simple body-centered tetragonal guest. This does not have the unexpectedly short Rb-Rb distances of the previously reported structure [U. Schwarz et al., Phys. Rev. Lett. 83, 4085 (1999)]. The ratio of the c-axis lattice parameters is strongly pressure dependent and approaches the commensurate value of 5/3 at the transition to phase V. A reversible broadening of the guest structure is observed below 16.5(2) GPa.
authors.affiliation: Department of Physics and Astronomy and Centre for Science at Extreme Conditions, The University of Edinburgh, Mayfield Road, Edinburgh, EH9 3JZ, United Kingdom.
authors.forename: M I
authors.initials: MI
authors.lastname: McMahon
authors.forename: S
authors.initials: S
authors.lastname: Rekhi
authors.forename: R J
authors.initials: RJ
authors.lastname: Nelmes