Nonorthogonal tight-binding model for germanium
Nonorthogonal tight-binding model for germanium
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DOI：
10.1103/physrevb.66.075212
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发表时间：
2002-08
影响因子：
3.7
通讯作者：
N. Bernstein;M. Mehl;D. Papaconstantopoulos
中科院分区：
文献类型：
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作者：
N. Bernstein;M. Mehl;D. Papaconstantopoulos
我们提出了一对非正交紧束缚（TB）模型内的NRL-TB方法的锗。一个使用sp 3的基础上，并优化总能量计算通过拟合的总能量和带结构的几个高对称性的晶格结构。另一种是使用一种基于量子化学的方法来精确地再现金刚石的晶格能带结构，包括三个导带。我们目前的测试的sp3 TB模型的散装性能，包括高对称性的晶格结构的能量和体积和金刚石晶格的弹性常数，声子和能带结构。我们还提出了点缺陷形成和弛豫能和低指数表面能和应力，其中许多还没有使用密度泛函理论（DFT）计算的结果，以及一些中等大小的集群。利用TB方法的计算效率，我们超越了标准密度泛函理论的能力，将其与分子动力学相结合来模拟Ge的有限温度性质。我们得到了很好的协议与实验的原子均方位移和熔点近似使用Linde-mann准则，以及线性热膨胀系数。在TB方法的效率的另一个演示中，我们提出了一个高角度扭曲晶界（GB）的结构和电子性质的结果。与DFT模拟一致，我们看到了一系列具有可比能量的结构，所有这些结构的电子态都位于带隙深处。与以前的工作相比，我们发现了一些不同的几何结构，在GB中的所有原子具有完美的四重配位。尽管有完美的协调，这些结构也有深的电子状态的差距，表明GB将是电活性。
We present a pair of nonorthogonal tight-binding (TB) models for germanium within the NRL-TB approach. One uses an sp 3 basis, and is optimized for total-energy calculations by fitting to the total energy and band structures of several high-symmetry lattice structures. The other uses an spuds basis to accurately reproduce the diamond lattice band structure, including three conduction bands. We present tests of the sp 3 TB model on bulk properties, including high-symmetry lattice structure energies and volumes and the diamond lattice elastic constants, phonons, and band structure. We also present results for point defect formation and relaxation energies and low index surface energies and stresses, many of which have not been calculated using the density-functional theory (DFT), as well as some medium size clusters. Taking advantage of the computational efficiency of the TB approach, we go beyond the capabilities of standard density-functional theory, combining it with molecular dynamics to simulate finite temperature properties of Ge. We get good agreement with experiment for the atomic mean-squared displacement and the melting point approximated using the Linde-mann criterion, as well as the linear thermal-expansion coefficient. In another demonstration of the efficiency of the TB approach, we present results for the structure and electronic properties of a high angle twist grain boundary (GB). In agreement with DFT simulation we see a range of structures with comparable energies, all with electronic states deep in the band gap. In contrast to previous work we find some different geometries with perfect fourfold coordination of all atoms in the GB. Despite the perfect coordination, these structures also have deep electronic states in the gap, indicating that the GB will be electrically active.