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arXiv 0907.5329cond-mat.mtrl-sci
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硅中氢分子的路径积分模拟

Molecular hydrogen in silicon: A path-integral simulation

Carlos P. Herrero, Rafael Ramirez

摘要:

采用正则系综下的路径积分分子动力学模拟研究了硅中的分子氢。在300 ~ 900 K范围内分析了这些点缺陷的变温特性。原子间的相互作用模型的紧束缚势拟合密度泛函计算。这些杂质的最稳定的位置被发现在间隙T网站,与氢分子在Si笼自由旋转。振动频率已获得从线性响应的方法,在有限温度下的原子位移的相关性的基础上。结果表明,在伸缩振动ω_s中存在很大的非谐效应,相对于谐波近似,它被软化了约300 cm^{-1}。旋转和振动之间的耦合导致ω_s随温度升高而显著减小。

英文摘要:

Molecular hydrogen in silicon has been studied by path-integral molecular dynamics simulations in the canonical ensemble. Finite-temperature properties of these point defects were analyzed in the range from 300 to 900 K. Interatomic interactions were modeled by a tight-binding potential fitted to density-functional calculations. The most stable position for these impurities is found at the interstitial T site, with the hydrogen molecule rotating freely in the Si cage. Vibrational frequencies have been obtained from a linear-response approach, based on correlations of atom displacements at finite temperatures. The results show a large anharmonic effect in the stretching vibration, omega_s, which is softened with respect to a harmonic approximation by about 300 cm^{-1}. The coupling between rotation and vibration causes an important decrease in omega_s for rising temperature.

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