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arXiv 0907.2175cond-mat.mtrl-sci
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立方SiC晶格参数的同位素效应

Isotope effects on the lattice parameter of cubic SiC

Carlos P. Herrero, Rafael Ramirez, Manuel Cardona

摘要:

采用路径积分分子动力学模拟方法,在NPT系综下研究了3C-SiC晶格常数与同位素质量的关系.这种计算方法允许定量和非微扰研究这种非谐效应。原子核被视为量子粒子通过紧束缚型势相互作用。在300 K时,含12 C和13 C的3C-SiC晶体的晶格参数之间的差值Δ a为2.1 × 10^{-4} A。Si同位素的影响较小,当用29 Si代替28 Si时,其值为3.5 x 10^{-5} A。PIMD模拟的结果解释在一个准谐波近似的晶格振动。

英文摘要:

Path-integral molecular dynamics simulations in the isothermal-isobaric (NPT) ensemble have been carried out to study the dependence of the lattice parameter of 3C-SiC upon isotope mass. This computational method allows a quantitative and nonperturbative study of such anharmonic effect. Atomic nuclei were treated as quantum particles interacting via a tight-binding-type potential. At 300 K, the difference Delta a between lattice parameters of 3C-SiC crystals with 12C and 13C amounts to 2.1 x 10^{-4} A. The effect due to Si isotopes is smaller, and amounts to 3.5 x 10^{-5} A when replacing 28Si by 29Si. Results of the PIMD simulations are interpreted in terms of a quasiharmonic approximation for the lattice vibrations.

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