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Compressibility and Structure of C 70

1995; Institute of Physics; Volume: 30; Issue: 8 Linguagem: Inglês

10.1209/0295-5075/30/8/005

1286-4854

A. A. Lundin, Alexander Soldatov, Bertil Sundqvist,

High-pressure geophysics and materials

The compressibility of C70 has been investigated by means of direct piston and cylinder measurements in the temperature range 150 to 365 K and up to 1 GPa. At 296 and 343 K we find a very rapid change of volume with pressure below 0.15 GPa. We tentatively interpret this as a continuous molecular reorientation with pressure, probably resulting in a transformation from a mixture of face-centred cubic (f.c.c.) and rhombohedral (r.h.) phases to mainly pure r.h. phase. At 365 K as well as at 236 K and below we see no anomalies indicating any structural or rotational anomalies in the pressure range investigated. The zero-pressure bulk modulus decreases with increasing temperature, from 13.1 GPa at 185 K to 7.9 GPa at 365 K. Our volumetric measurements confirm a recently proposed phase diagram for C70.