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arXiv 1406.2600physics.comp-ph
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基于谱有限元离散的Kohn-Sham密度泛函理论大规模计算的次二次尺度子空间投影方法

A subquadratic-scaling subspace projection method for large-scale Kohn-Sham density functional theory calculations using spectral finite-element discretization

Phani Motamarri, Vikram Gavini

摘要:

我们提出了一个子空间投影技术进行大规模的Kohn-Sham密度泛函理论计算使用光谱有限元离散。所提出的方法处理金属和绝缘材料在一个单一的框架,并适用于赝势以及全电子计算。该方法的主要思想包括:(i)采用一种适合于网格自适应的高阶谱有限元基;(ii)利用Chebyshev滤波器构造一个子空间,该子空间是给定自洽场迭代中所占据的特征空间的近似;(iii)利用局部化过程构造一个跨越Chebyshev滤波子空间的非正交局部化基;(iv)根据在非正交定域基中表示的子空间投影哈密顿量使用费米算子展开来计算相关量,如密度矩阵、电子密度和能带能量。我们证明了基准系统的方法,涉及赝势计算金属铝纳米簇高达3430个原子和绝缘烷烃链高达7052个原子,以及硅纳米簇高达3920个电子的全电子计算的准确性和效率。基准研究表明,可以获得与化学精度相称的精度,并观察到的范围内的材料系统的研究与系统大小的次二次缩放。特别地,对于烷烃链-观察到接近线性缩放,而对于铝纳米簇-观察到缩放为$\mathcal{O} (N^{1.46})$。对于硅纳米团簇的全电子计算,电子数的标度计算为$\mathcal{O} (N^{1.75})$。此外,显着的计算节省已实现与参考计算方面的建议的方法。

英文摘要:

We present a subspace projection technique to conduct large-scale Kohn-Sham density functional theory calculations using spectral finite-element discretization. The proposed method treats both metallic and insulating materials in a single framework, and is applicable to both pseudopotential as well as all-electron calculations. The key ideas involved in the method include: (i) employing a higher-order spectral finite-element basis that is amenable to mesh adaption; (ii) using a Chebyshev filter to construct a subspace which is an approximation to the occupied eigenspace in a given self-consistent field iteration; (iii) using a localization procedure to construct a non-orthogonal localized basis spanning the Chebyshev filtered subspace; (iv) using a Fermi-operator expansion in terms of the subspace-projected Hamiltonian represented in the non-orthogonal localized basis to compute relevant quantities like the density matrix, electron density and band energy. We demonstrate the accuracy and efficiency of the approach on benchmark systems involving pseudopotential calculations on metallic aluminum nano-clusters up to 3430 atoms and on insulating alkane chains up to 7052 atoms, as well as all-electron calculations on silicon nano-clusters up to 3920 electrons. The benchmark studies revealed that accuracies commensurate with chemical accuracy can be obtained, and a subquadratic-scaling with system size was observed for the range of materials systems studied. In particular, for the alkane chains---close to linear-scaling is observed, whereas, for aluminum nano-clusters---the scaling is observed to be $\mathcal{O} (N^{1.46})$. For all-electron calculations on silicon nano-clusters, the scaling with the number of electrons is computed to be $\mathcal{O} (N^{1.75})$. Furthermore, significant computational savings have been realized with the proposed approach with respect to reference calculations.

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