Ls. Fomenko et al., CORRELATION OF LOW-TEMPERATURE MICROPLAST ICITY ANOMALIES WITH STRUCTURE TRANSFORMATIONS IN C-60 CRYSTALS, Fizika nizkih temperatur, 21(4), 1995, pp. 465-468
Structure, microhardness and slip systems were studied on C-60 crystal
s of high purity in the temperature range 30-290 K, which includes the
fcc --> sc phase transition at T-c = 260 K and the orientational glas
s region T < 100 K. A step-like change of both the lattice parameter a
nd the microhardness was recorded when passing through T-c, as well as
the formation of slip lines near the indentations in both phases. The
slip system <110>{111}, operative at room temperature in the FEC phas
e, is shown to retain its activity below T-c, in the sc phase. In the
region where the orientation glass is formed, we have found a kink-lik
e anomaly on the microhardness vs temperature curve; this anomaly corr
elates with a weak anomaly in the temperature dependence of the lattic
e parameter. Assumptions are Formulated concerning the chancier ol the
dislocation motion in C-60 crystals, which make it possible to explai
n the microplasticity anomalies observed.