High-pressure synthesis, structural and Raman studies of a two-dimensional polymer crystal of C60
Laboratoire de Physique des SolidesUMR 8502 du CNRS, Bâtiment 510, Université Paris-Sud, 91405 Orsay, France
2 Department of Experimental Physics, Umeå University, 90187 Umeå, Sweden
Published online: 15 May 2000
Two-dimensional polymerisation of a C60 single crystal has been obtained under high-pressure high temperature conditions (700 K - 2 GPa). Crystalline order is preserved but the crystal splits into variants (orientational domains). The analysis of X-ray diffraction and Raman spectroscopy data reveals that the polymer crystal is primarily tetragonal with some admixture of rhombohedral phase. Furthermore, Raman spectroscopy gives evidence for additional C60-C60 dimers, which are probably disordered. For the tetragonal phase, it is shown that successive polymer layers are rotated by 90° about the stacking axis, according to the P42/mmc space group symmetry. The structure of the rhombohedral phase is also clarified. The role of the interlayer interactions in stabilising the two-dimensional polymer phases of C60 is discussed.
PACS: 61.48.+c – Fullerenes and fullerene-related materials / 61.50.Ks – Crystallographic aspects of phase transformations; pressure effects
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2000