J. Phys. IV France
Volume 12, Numéro 9, November 2002
Page(s) 233 - 234

J. Phys. IV France
12 (2002) Pr9-233
DOI: 10.1051/jp4:20020402

Unusual 2 k   CDW state with enhanced charge ordering in P-(BEDT-TTF) AsF  and PF6

Y. Nogami1 and T. Mori2

1  Department of Physics, Okayama University, 3-1-1 Tsushimanaka, Okayama 700-8530, Japan
2  Department of Organic and Polymeric Materials, Tokyo Institute of Technology, Okayama, Tokyo 152-8552, Japan

X-ray superstructure analyses of the $2k_{\rm F}$ CDW states for two-dimensional organic compounds $\beta$-(BEDT-TTF) 2PF 6 and AsF 6 were presented Molecular ionicity of BEDT-TTF was evaluated with both intramolecular bond lengths and molecular shape. Strong bending of quasi-neutd BEDT-TTF molecules coupled with the enhanced amplitude of charge modulation was observed Conformational ordering of the terminal ethylenes of BEDT-TTF molecules anddmeriiation between quasi-ionic BEJYI-TTF molecules were also observed These characteristic indicates this CDW is not Peierls-Frohlich type but mupled with the internal degree of the molecular shape and possibly the intersite Coulomb repulsion.

© EDP Sciences 2002