The effect of approximating some molecular integrals in coupled-cluster calculations: fundamental frequencies and rovibrational spectroscopic constants for isotopologues of cyclopropenylidene
The effect of approximating some molecular integrals in coupled-cluster calculations: fundamental frequencies and rovibrational spectroscopic constants for isotopologues of cyclopropenylidene
复制标题
耦合簇计算中一些分子积分的近似效果：环丙烯亚基同位素体的基频和振动光谱常数
DOI：
10.1080/00268970902769455
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发表时间：
2009
影响因子：
1.7
通讯作者：
Christopher E. Dateo
中科院分区：
文献类型：
--
作者：
Timothy J. Lee;Xinchuan Huang;Christopher E. Dateo
本文研究了在单、双耦合团簇理论（CCSD（T））中近似三、四虚分子轨道积分对计算高阶性质，特别是计算分子四次力场和光谱常数的影响。该方法以前提出过，但只研究了二阶和低阶性质。它表明，以前达到的结论基本上是不变的移动到高阶属性。也就是说，逼近所选积分对CCSD（T）计算的准确性基本没有影响，并且逼近积分引起的误差比单粒子基组缺陷引起的残余误差小得多。这种方法的优点在于，它显著减少了执行CCSD（T）计算所需的数据量，从而减少了与大规模并行分布式存储器算法中的输入/输出操作和消息传递相关联的计算要求。这些节省对于大基组计算特别重要，其中数据的减少可以高达1000个未占据分子轨道的三个数量级。该方法进行了测试，通过计算四次力场，振动频率和光谱常数的环丙烯叉和同位素。我们最好的结果与现有的实验数据的比较表明，理论和实验之间的良好协议。希望本文提出的环丙烯叉和同位素的理论光谱数据在解释未来的实验室实验和天文观测中是有用的。
The effect of approximating the three- and four-virtual molecular orbital integrals in single and double coupled-cluster theory including a perturbational correction for connected triple excitations [CCSD(T)] is investigated for the calculation of higher-order properties, specifically the calculation of a molecular quartic force field and spectroscopic constants. The approach was proposed previously, but investigated for only second- and lower-order properties. It is shown that the conclusions reached previously are essentially unchanged on moving to higher-order properties. That is, approximating the selected integrals has essentially no effect on the accuracy of CCSD(T) calculations, and the error due to approximating integrals is much smaller than the residual error due to one-particle basis set deficiencies. The advantage of this approach is that it significantly reduces the amount of data needed to perform CCSD(T) calculations, thereby reducing computational requirements associated with input/output operations and message passing in massively parallel, distributed memory algorithms. These savings are particularly important for large basis set calculations where the reduction in data can be as high as three orders of magnitude for ∼1000 unoccupied molecular orbitals. The approach was tested by computing the quartic force field, vibrational frequencies, and spectroscopic constants of cyclopropenylidene and isotopologues. Comparison of our best results with available experimental data shows excellent agreement between theory and experiment. It is hoped that the theoretical spectroscopic data presented herein for cyclopropenylidene and isotopologues is useful in the interpretation of future laboratory experiments and astronomical observations.