中文摘要：

采用MedeA软件包优化了一系列不同直径的碳纳米管的结构,并计算了相关声子谱和声子态密度,进一步计算了碳纳米管的热力学性质。结果表明碳纳米管的直径和温度对其热力学性质有影响。碳纳米管的直径越大,其生成能和总能量就越低,即稳定性越好。在低温时,直径对碳纳米管的热力学性质的影响较小;高温时,碳纳米管的热力学性质Cv（T）、S^0（T）、–A（T）及Evib（T）随直径增大呈现升高趋势,而E（T）和G（T）则随碳纳米管的直径增大呈现降低趋势。

英文摘要：

The structures of single-walled carbon nanotubes with different diameter were optimized by MedeA program package. The phonon spectra and the density of state ofphonon were used to simulate the thermodynamics properties of the carbon nanotubes. The results showed that the carbon nanotube diameter and temperature affect the thermodynamic properties. The larger the diameter of carbon nanotube is, the lower the formation and the total energy it has, that is, the better stability is it. At low temperature, diameter has little effect on thermodynamics properties of CNTs. It is a climbing tendency in Cv （T）, S^0（T）, -A（T） and Evib （T） with diameter, while a falling tendency in E（ T ） and G（ T ）.