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首页> 外文期刊>The Journal of Chemical Physics >Local ab initio methods for calculating optical band gaps in periodic systems. I. Periodic density fitted local configuration interaction singles method for polymers
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Local ab initio methods for calculating optical band gaps in periodic systems. I. Periodic density fitted local configuration interaction singles method for polymers

机译：用于计算周期性系统中光学带隙的局部从头计算方法。一，聚合物的周期性密度拟合局部构型相互作用单方法

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摘要

We present a density fitted local configuration interaction singles (CIS) method for calculating optical band gaps in 1D-periodic systems. The method is based on the Davidson diagonalization procedure, carried out in the reciprocal space. The one-electron part of the matrix-vector products is also evaluated in the reciprocal space, where the diagonality of the Fock matrix can be exploited. The contraction of the CIS vectors with the two electron integrals is performed in the direct space in the basis of localized occupied (Wannier) and virtual (projected atomic) orbitals. The direct space approach allows to utilize the sparsity of the integrals due to the local representation and locality of the exciton. The density fitting approximation employed for the two electron integrals reduces the nominal scaling with unit cell size to O(N~4). Test calculations on a series of prototypical systems demonstrate that the method in its present stage can be used to calculate the excitonic band gaps of polymers with up to a few dozens of atoms in the cell. The computational cost depends on the locality of the exciton, but even relatively delocalized excitons occurring in the polybiphenyl in the parallel orientation, can be routinely treated with this method.
机译：我们提出了一种密度拟合局部配置相互作用单（CIS）方法来计算一维周期系统中的光学带隙。该方法基于在倒数空间中执行的Davidson对角化过程。矩阵向量乘积的单电子部分也在倒数空间中进行评估，在倒数空间中可以利用Fock矩阵的对角线。具有两个电子积分的CIS向量的收缩是在直接空间中根据局部占据（Wannier）和虚拟（投射原子）轨道进行的。直接空间方法由于激子的局部表示和局部性而允许利用积分的稀疏性。两个电子积分采用的密度拟合近似将标称比例随晶胞尺寸减小至O（N〜4）。在一系列原型系统上的测试计算表明，该方法在其当前阶段可用于计算单元中具有多达几十个原子的聚合物的激子能带隙。计算成本取决于激子的位置，但是即使在平行方向上出现在聚联苯中的相对离域的激子，也可以使用此方法进行常规处理。

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