W1X-1 and W1X-2: W1-Quality Accuracy with an Order of Magnitude Reduction in Computational Cost
W1X-1 and W1X-2: W1-Quality Accuracy with an Order of Magnitude Reduction in Computational Cost
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DOI：
10.1021/ct300632p
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发表时间：
2012-11-01
影响因子：
5.5
通讯作者：
Radom, Leo
中科院分区：
文献类型：
--
作者：
Chan, Bun;Radom, Leo
我们已经研究了一些方法，以减少计算要求的W1 W和W1-F12程序，同时保持准确性。一个关键的发现是，MP2/cc-pCVTZ提供了一个可靠的手段，在W1型程序的背景下，可以忽略不计的成本的核心相关性的影响进行评估。这大大降低了总体计算成本，因为对于W1 w和W1-F12而言，堆芯相关性的计算是最耗时的步骤。对于效价CCSD（T）/CBS的评估，我们发现，截断的扩散函数集导致显着节省时间，只有轻微的性能恶化。为了消除进行CCSD计算的需要，我们保留了W1-F12中采用的方法，即使用显式相关程序。我们得到的程序被称为W1 X-1和W1 X-2（其中X指的是eXplplanetary相关程序），其中，W1 X-1协议需要两个CGSD-F12 b加上两个CCSD（T）计算，以获得价CCSD（T）/CBS能量分量，与W1-F12一样。另一方面，W1 X-2程序只需要两次CCSD（T）F12 b计算来评估CCSD（T）/CBS，因此比W1 X-1便宜。事实上，W1 X-2协议的计算量比W1 w低一个数量级，成本比W1-F12低80%。对W1 X-1和W1 X-2程序的广泛评估表明，W1 X-1性能良好，几乎在所有情况下都优于W1 w和W1-F12。的W1 X-2方法给出了相当好的结果，大多数热化学性质，但热的形成碳氟化合物和络合能的氟化氢集群代表显着的例外。
We have examined a number of approaches for reducing the computational requirements of the W1w and W1-F12 procedures, while maintaining the accuracy. A key finding is that MP2/cc-pCVTZ provides a reliable means for the evaluation of core correlation effects at a cost that is negligible in the context of W1-type procedures. This greatly reduces the overall Computational cost, since calculations for core correlation represent the most time-consuming steps for both W1w and W1-F12. For the evaluation of valence CCSD(T)/CBS, we find that truncation of the sets of diffuse functions leads to a significant savings in time, with only a minor deterioration in the performance. In order to eliminate the need to carry out CCSD calculations With a quadruple-zeta basis set, we have maintained the approach employed in W1-F12, namely the use of explicitly correlated procedures. Our resulting procedures are termed W1X-1 and W1X-2 (where the X refers to the eXplicitly correlated procedures), Of these, the W1X-1 protocol requires two CGSD-F12b plus two CCSD(T) calculations to obtain the valence CCSD(T)/CBS energy component, as with W1-F12. The W1X-2 procedure, On the other hand, requires only two CCSD(T) F12b calculations for the evaluation Of CCSD(T)/CBS and is therefore less expensive than W1X-1. Indeed, the W1X-2 protocol is an order Of magnitude less computationally demanding than W1w and similar to 80% less costly than W1-F12. Extensive assessment of the W1X-1 and W1X-2 procedures shows that W1X-1 performs well and comparably to W1w and W1-F12 in virtually all cases. The W1X-2 method gives equivalently good results for most thermochemical properties, but the heats of formation of fluorocarbons and complexation energies of hydrogen fluoride clusters represent notable exceptions.