科研之友
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摘要
The modified Nose-Hoover (NH) thermostat incorporated with molecular dynamics calculation is applied to evaluate the mechanical properties of multi-layered graphene structures at atmospheric pressure, including Young's modulus, shear modulus, Poisson's ratio, specific heats, linear coefficient of thermal expansion (CTE) and thermal conductivity. The thermostat method takes into account the contribution of phonons by virtue of the vibrational energy of the lattice and the zero-point energy, thereby providing a better prediction of the low temperature thermodynamic properties. The focuses of this study are placed on exploring their temperature, size, chirality and layer number dependences. The validity of the calculations is further demonstrated by comparing the calculated results with those derived from the existing thermostats, namely, the standard NH, Nose-Hoover chain (NHC), "massive" NHC and velocity-rescaling thermostats, and also with the literature experimental and theoretical data. It was found that the calculated mechanical properties of the graphene sheets agree well with the published experimental and theoretical results. The results also show that their Young's modulus, shear modulus, linear CTE and Poisson's ratio tend to decrease with the increase of temperature, size and layer number, where the linear CTE would eventually converge to that of the bulk graphite. Besides, the heat capacity and thermal conductivity at low temperatures show the high temperature dependences, i.e., the third and lambda (lambda = 2-3) power of temperature, which are more consistent with that obtained from Debye model.
- 出版日期2016-5
- 单位清华大学
