Pressure evolution of the structure of

¹ School of Chemistry, Physics and Environmental Science University of Sussex - Brighton BN1 9QJ, UK
² Department of Chemistry, University of Cambridge Cambridge CB2 1EW, UK
³ Institute of Materials Science, NCSR "Demokritos" 153 10 Ag. Paraskevi, Athens, Greece
⁴ Japan Advanced Institute of Science and Technology Tatsunokuchi, Ishikawa 923-1292, Japan
⁵ European Synchrotron Radiation Facility F-38043 Grenoble, France

Received: 16 February 2001
Accepted: 12 July 2001

Abstract

The structural features of the ammoniated (NH₃)K₃C₆₀ fulleride are studied by synchrotron X-ray powder diffraction as a function of pressure to 6.7 GPa. A superstructure appears at ~1 GPa as a result of orientational ordering of both the C₆₀ and K⁺-NH₃ units (orthorhombic symmetry, space group Fddd). The pressure evolution of the lattice constants reveals a highly compressible, strongly anisotropic structure. The centre-to-centre interfullerene separations of ~10.40 Åin the basal plane are comparable to those in the superconducting cubic analogue, RbCs₂C₆₀ and evidently sufficiently short to drive the system superconducting, despite its low crystal symmetry.