Transmission electron diffraction study of C70 phase transformation at low temperature

Abstract
C70 grown on a NaCl substrate is observed by transmission electron microscopy (TEM) at low temperature (104 K). New spots that appear reproducibly in the electron diffraction (ED) at low temperature can be indexed as (m±1/2, n±1/2, 0) (m, n: integer) in a [001]hcp projection. The lattice constant a is lower at low temperature and the reduction ratio is a104 K/a300 K=1.02/1.06 nm=0.96±0.02, which is much lower than the value reported for C60. The ED of the low-temperature phase is observed below about 260 K, and an intermediate state is also detected in this temperature range.