Efficient implementation of core-excitation Bethe-Salpeter equation calculations
Efficient implementation of core-excitation Bethe-Salpeter equation calculations
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DOI：
10.1016/j.cpc.2015.08.014
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发表时间：
2015-12-01
影响因子：
6.3
通讯作者：
Rehr, J. J.
中科院分区：
文献类型：
--
作者：
Gilmore, K.;Vinson, John;Rehr, J. J.
我们提出了一个有效的实现Bethe-Salpeter方程（BSE）方法获得核心水平的光谱，包括X射线吸收（XAS），X射线发射（XES），共振和非共振非弹性X射线散射光谱（N/RIXS）。计算是基于密度泛函理论（OFT）的电子结构产生的ABINIT或QuantumESTEGO，平面波的基础上，赝势代码。这种电子结构通过包含GW自能而得到改善。投影增广波技术被用来评估芯能级和带态之间的过渡矩阵元素。最终的两个粒子散射状态得到的NIST核心级的BSE求解器（NBSE）。我们之前已经报道了这种实现，我们将其称为OCEAN（从从头算电子结构和NBSE获得核心激发）（Vinson等人，2011年）。在这里，我们提出了额外的效率，使我们能够评估系统的光谱比以前可能的大十倍，包含多达几千个电子。这些改进包括最佳基函数的实现，降低了初始OFT计算的成本，更完整的并行化的筛选计算和BSE哈密顿量的行动，和各种内存减少，缩放证明SrTiO 3的超晶胞和有机发光分子三-（8-羟基喹啉）铝（Alq（3））的示例光谱。执行大规模光谱计算的能力对于研究稀释或非周期性系统（例如掺杂材料、非晶系统或复杂纳米结构）特别有利。(C)2015 Elsevier B. V.版权所有。
We present an efficient implementation of the Bethe-Salpeter equation (BSE) method for obtaining core-level spectra including X-ray absorption (XAS), X-ray emission (XES), and both resonant and non-resonant inelastic X-ray scattering spectra (N/RIXS). Calculations are based on density functional theory (OFT) electronic structures generated either by ABINIT or QuantumESPRESSO, both plane-wave basis, pseudopotential codes. This electronic structure is improved through the inclusion of a GW self energy. The projector augmented wave technique is used to evaluate transition matrix elements between core-level and band states. Final two-particle scattering states are obtained with the NIST core-level BSE solver (NBSE). We have previously reported this implementation, which we refer to as OCEAN (Obtaining Core Excitations from Ab initio electronic structure and NBSE) (Vinson et al., 2011). Here, we present additional efficiencies that enable us to evaluate spectra for systems ten times larger than previously possible; containing up to a few thousand electrons. These improvements include the implementation of optimal basis functions that reduce the cost of the initial OFT calculations, more complete parallelization of the screening calculation and of the action of the BSE Hamiltonian, and various memory reductions, Scaling is demonstrated on supercells of SrTiO3 and example spectra for the organic light emitting molecule Tris-(8-hydroxyquinoline)aluminum (Alq(3)) are presented. The ability to perform large-scale spectral calculations is particularly advantageous for investigating dilute or non-periodic systems such as doped materials, amorphous systems, or complex nano-structures. (C) 2015 Elsevier B.V. All rights reserved.