Highly accurate O(N) method for delocalized systems
Highly accurate O(N) method for delocalized systems
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适用于离域系统的高精度 O(N) 方法
DOI：
10.1007/s00214-011-1011-z
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
F.L.Gu
中科院分区：
文献类型：
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作者：
Y.Aoki;O.Loboda;K.Liu;M.A.Makowski;F.L.Gu
在我们的小组中开发的伸长方法是一种从头计算方法，具有高效率和高精度（与传统计算相比，总能量误差<10 − 8au/原子），可应用于任何一维（聚合物），二维（表面）或三维（固体材料）系统。然而，对于强离域系统，目标整个系统的原始伸长方法的准确性下降了约两个数量级的总能量相比，由较早实施的版本的伸长方法nondelocalized系统获得的值。伸长法和传统方法总能量之间的相对较小的差异（10 − 6 - 10 − 8au）导致了二阶超极化率γ的更严重的误差，特别是在伴随着强离域的纳米尺度系统中。为了解决这个问题，我们已经纳入了一个简单的校正技术的基础上附加的“轨道基础”的“区域基础”在我们原来的伸长方法的程序。一些不太定域的轨道被纳入与攻击分子的相互作用中。这种治疗已被应用到一些模型纳米和生物系统，以前已经表现出较强的离域性，并在非强离域系统获得的能量的高精度被保留，即使是强离域系统，无论是能量和第二超极化率。这是一个重大的突破，现在扩展了系统的伸长方法可以用来计算和预测二阶非线性光学性质的离域系统。
The elongation method, developed in our groups, is an ab initio method approaching order O(N) type scalability with high efficiency and high accuracy (error <10−8au/atom in total energy compared to the conventional calculation) that can be applied to any one-dimensional (polymer), two-dimensional (surface) or three-dimensional (solid material) systems. For strongly delocalized systems, however, the accuracy of the original elongation method for the targeted entire systems declines by approximately two orders of magnitude in the total energy as compared to the value obtained by the earlier implemented version of the elongation method for nondelocalized systems. The relatively small differences (10−6–10−8au) between the elongation method and conventional method total energies have caused more serious errors in the second hyperpolarizability,γ, especially in nano-scale systems which have accompanying strong delocalization. In order to solve this problem, we have incorporated a simple correction technique based on an additional “orbital basis” to the “region basis” in our original elongation method procedures. Some not so-well-localized orbitals are incorporated into the interaction with the attacking molecule. This treatment has been applied to some model nano- and bio-systems that previously have shown strong delocalization, and the high accuracy in the energy obtained for nonstrongly delocalized systems was retained even for the strongly delocalized systems, both for the energies and for the second hyperpolarizabilities. This is a major breakthrough and now expands the systems for which the elongation method can be used to calculate and predict second-order nonlinear optical properties for delocalized systems.