Slip systems in C 60 single crystals

Abstract

A behavior of plastic deformations of C60 single crystals was examined using the microindentation technique. Not only slip lines but also dislocation etch pits were observed around the indentation on the crystal surface. It is confirmed that the slip systems in C60 single crystals are {111}〈110〉 in a temperature range of 240 K to 450 K. This means that, even in a simple cubic phase below a phase transition temperature of ∼260 K, the slip systems are the same as a face-centered-cubic phase.

Photo-illumination hardening of C60 crystals

“…One is discontinuous change in the hardness at a temperature of 260 K, which was also observed by Fomenko et al 12 Such a marked change in hardness is due to the phase transition of the orientational-orderinginduced face-centered-cubic to simple cubic phase. 19 The other is an anomalous behavior of the hardness at temperatures higher than 300 K: the hardness increases with increasing temperature and reaches a maximum at 380 K. It is not plausible that the anomalous behavior of the hardness is due to the change in the slip system of C 60 crystals because no change in the ͕111͖͗110͘ slip system of C 60 crystals was observed in a temperature range of 240-450 K. 12,20 In the measurement of the hardness at each temperature in Fig. 6͑a͒, the crystal surface was exposed with white light ͑2.0 mW/mm 2 ) from a halogen lamp for about 1 minute to observe the indentations with the CCD camera.…”

Temperature and photopolymerization effects in microhardness of C70 crystals

“…However, the microscopic observation of the slip bands produced by the indentation has shown the activity of only slip system of ͕111͖͗110͘ type in both fcc and sc. 15,16 It seems, therefore, that the strong temperature dependence of the hardness at temperatures lower than 260 K is due to the interaction between dislocations and pentagonal and hexagonal orientations of C 60 molecules rather than the change in the magnitude of Burgers vector during the phase transition.…”

Estimate of theoretical shear strength of C60 single crystal by nanoindentation

“…The critical resolved shear stress is then computed for the octahedral slip systems h011i 111 f g. These were earlier identified by X-ray topography of indents on C 60 crystals [36]. Furthermore, the activation of the octahedral slip systems was determined by studying the pattern of slip traces, which were formed around the indents at loads exceeding 0.1-0.2 N [37,38].…”