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Accuracy of Low-level Surface in Hierarchical Construction of Potential Energy Surface
Chun-rui Wang, Dong H. Zhang*
State Key Laboratory of Molecular Reaction Dynamics & Center for Theoretical and Computational Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
Abstract:
The effects of low-level PES on the overall accuracy of the final surface constructed by using hierarchical construction were investigated with the constructions of a number of global surfaces for the H3 system at UHF (UMP2, DFT-B3LYP, UCCSD(T))/vtz, and UCCSD(T)/avqz levels of theory. The total reaction probabilities for the H+H2 reaction calculated on these surfaces revealed that the accuracy of UCCSD(T)/avqz surface is very close to the well-known BKMP2 surface, while the UCCSD(T)/vtz PES has a slightly higher barrier. In contrast, the low-level theories (UHF, UMP2, DFT-B3LYP) with vtz basis set can only provide a qualitative description of this simplest reaction despite the fact that they are widely used to study reactions in complex systems. On the other hand, although these theories are not accurate on describing the reaction, they can be used to provide the low-level PESs for hierarchical construction of the UCCSD(T)/avqz PES with the number of UCCSD(T)/avqz energies substantially reduced.
Key words:  Hierarchical construction scheme, Accuracy of potential energy surface, Three-dimensional cubic spline
FundProject:
分级构建势能面中低级别势能面精度
王春锐, 张东辉*
中国科学院大连化学物理研究所分子反应动力学国家重点实验室和理论与计算化学中心,大连116023
摘要:
通过构建一系列H3体系的UHF(UCCSD(T)、DFT-B3LYP、UMP2)/vtz和UCCSD(T)/avqz级别的势能面,研究了分级构建方案中低级别势能面对最终势能面精度的影响. 基于这些势能面计算得到的H+H2反应的总反应几率表明,UCCSD(T)/avqz势能面的精度与著名的BKMP2势能面非常接近,得到的势垒略微偏高. 作为对比,尽管低级别理论(UHF、UMP2、DFT-B3LYP)加上vtz基组在复杂体系中得到了广泛地应用,但是它们对这个最简单的反应只能提供一个定性的描述. 另一方面,尽管这些理论不能准确描述这个反应,但是可以应用它们来得到分级构建中的低级别势能面,从而建立精度级别为UCCSD(T)/avqz的势能面,使得所需要的UCCSD(T)/avqz能量的数目大大减少.
关键词:  分级构建方案,势能面精度,三次样条插值
DOI:10.1088/1674-0068/25/02/186-190
分类号: