Finite-temperature quasicontinuum method for multiscale analysis of silicon nanostructures
Finite-temperature quasicontinuum method for multiscale analysis of silicon nanostructures
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DOI：
10.1103/physrevb.74.064110
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发表时间：
2006-08
影响因子：
3.7
通讯作者：
Zhi Tang;Huijuan Zhao;Gang Li;N. Aluru
中科院分区：
文献类型：
--
作者：
Zhi Tang;Huijuan Zhao;Gang Li;N. Aluru
在本文中，我们扩展了准连续谱方法，用于有限温度下硅纳米结构的多尺度分析。拟连续介质方法使用经典的连续介质力学框架，但系统的本构响应是通过采用原子描述来确定的。对于等温条件下的有限温度固体系统，本构响应由亥姆霍兹自由能密度确定。亥姆霍兹自由能密度的静态部分直接从原子间势中获得，而振动部分则利用量子力学晶格动力学理论计算。具体来说，我们研究了三种准调和模型，即实空间准调和模型、局部准调和模型和倒易空间准调和模型，来计算振动自由能。使用有限温度准连续谱方法，我们计算了温度和应变对声子态密度、声子 Gruneisen 参数和 Tersoff 硅弹性特性的影响。我们还计算了硅纳米结构对各种外部载荷的机械响应，并将结果与分子动力学模拟进行了比较。
In this paper, we extend the quasicontinuum approach for a multiscale analysis of silicon nanostructures at finite temperature. The quasicontinuum method uses the classical continuum mechanics framework, but the constitutive response of the system is determined by employing an atomistic description. For finite-temperature solid systems under isothermal conditions, the constitutive response is determined by using the Helmholtz free energy density. The static part of the Helmholtz free energy density is obtained directly from the interatomic potential while the vibrational part is calculated by using the theory of quantum-mechanical lattice dynamics. Specifically, we investigate three quasiharmonic models, namely the real space quasiharmonic model, the local quasiharmonic model, and the reciprocal space quasiharmonic model, to compute the vibrational free energy. Using the finite-temperature quasicontinuum method, we compute the effect of the temperature and strain on the phonon density of states, phonon Gruneisen parameters, and the elastic properties of the Tersoff silicon. We also compute the mechanical response of silicon nanostructures for various external loads and the results are compared to molecular dynamics simulations.