Accurate ionic forces and geometry optimization in linear-scaling density-functional theory with local orbitals
Accurate ionic forces and geometry optimization in linear-scaling density-functional theory with local orbitals
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DOI：
10.1103/physrevb.83.195102
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发表时间：
2011-05-02
影响因子：
3.7
通讯作者：
Mostofi, Arash A.
中科院分区：
文献类型：
--
作者：
Hine, Nicholas D. M.;Robinson, Mark;Mostofi, Arash A.
密度泛函理论（DFT）模拟的线性标度方法是根据真实的空间中的定域轨道来制定的，而不是传统方法的离域本征态。在局域轨道方法中，相对于传统的DFT，期望的性质可能会在一定程度上丢失，例如系统的总能量相对于小位移的平移不变性和势能面的光滑性。这对计算精确的离子力和几何形状有影响。在这项工作中，我们提出的结果从ONETEP，我们的线性标度方法的基础上本地化轨道在真实的空间。使用psinc函数作为基础基组和局部轨道的动态优化会导致平滑的势能表面，这与使用赫尔曼-费曼定理计算的离子力一致。这使得能够执行精确的几何优化。硅表面重建的结果，沿着与三个示例系统演示了性能的准牛顿几何优化算法：一个有机zwitteres，一个点缺陷的离子晶体，和半导体纳米结构。
Linear scaling methods for density-functional theory (DFT) simulations are formulated in terms of localized orbitals in real space, rather than the delocalized eigenstates of conventional approaches. In local-orbital methods, relative to conventional DFT, desirable properties can be lost to some extent, such as the translational invariance of the total energy of a system with respect to small displacements and the smoothness of the potential-energy surface. This has repercussions for calculating accurate ionic forces and geometries. In this work we present results from ONETEP, our linear scaling method based on localized orbitals in real space. The use of psinc functions for the underlying basis set and on-the-fly optimization of the localized orbitals results in smooth potential-energy surfaces that are consistent with ionic forces calculated using the Hellmann-Feynman theorem. This enables accurate geometry optimization to be performed. Results for surface reconstructions in silicon are presented, along with three example systems demonstrating the performance of a quasi-Newton geometry optimization algorithm: an organic zwitterion, a point defect in an ionic crystal, and a semiconductor nanostructure.