论文标题
抛光黄金标准：轨道选择在CCSD（T）振动频率预测中的作用
Polishing the Gold Standard: The Role of Orbital Choice in CCSD(T) Vibrational Frequency Prediction
论文作者
论文摘要
尽管CCSD（T）具有自旋限制的Hartree-fock（RHF）轨道长期以来因其准确描述封闭壳相互作用的能力而受到称赞，但开放式壳物种上CCSD（T）的性能更为不稳定，尤其是在使用自旋无限制的HF（UHF（UHF）参考时）。先前的研究表明，当使用Brueckner或Kohn-Sham密度功能理论（DFT）轨道等一组非HF分子轨道时，对开放壳系统的处理得到了改善。受到正则轨道优化的二阶Møller-plesset扰动理论（$κ$ -OOMP2）作为MP3的参考轨道的成功启发，我们研究了$κ$ -OOMP2轨道和各种DFT轨道的使用，以及各种DFT轨道，作为CCSD的36级平台（t）cccs ccs的参考轨道，以均匀的轨道轨道旋转（t）的距中性，6个阳离子，1个阴离子）和59种开放壳双子态物种（38个中性，15个阳离子，6个阴离子）。在这种情况下，使用$κ$ -OOMP2轨道减轻了UHF轨道和OOMP2轨道的困难病例。删除2个具有模棱两可的实验数据的多余系统和12个系统会留下修剪的数据集。在修剪数据集的总体性能突出显示了CCSD（T），具有B97轨道参考（CCSD（T）：B97），CCSD（T），具有$κ$ -OOMP2轨道参考（CCSD（ccsd（t）：$κ$ -OOMP2）和b97m-b97m-rv（t） with RMSDs of 8.48 cm$^{-1}$ and 8.50 cm$^{-1}$, and 8.75 cm$^{-1}$ respectively, outperforming CCSD(T):UHF by nearly a factor of 5. Moreover, the performance on the closed- and open-shell subsets show these methods are able to treat open-shell and closed-shell systems with comparable accuracy and robustness. $κ$ -OOMP2轨道的使用也已证明可用于诊断可以阻碍CCSD（t）可靠性的多等法特征。
While CCSD(T) with spin-restricted Hartree-Fock (RHF) orbitals has long been lauded for its ability to accurately describe closed-shell interactions, the performance of CCSD(T) on open-shell species is much more erratic, especially when using a spin-unrestricted HF (UHF) reference. Previous studies have shown improved treatment of open-shell systems when a non-HF set of molecular orbitals, like Brueckner or Kohn-Sham density functional theory (DFT) orbitals, is used as a reference. Inspired by the success of regularized orbital-optimized second-order Møller-Plesset perturbation theory ($κ$-OOMP2) orbitals as reference orbitals for MP3, we investigate the use of $κ$-OOMP2 orbitals and various DFT orbitals as reference orbitals for CCSD(T) calculations of the corrected ground-state harmonic vibrational frequencies of a set of 36 closed-shell (29 neutrals, 6 cations, 1 anion) and 59 open-shell diatomic species (38 neutrals, 15 cations, 6 anions). The use of $κ$-OOMP2 orbitals in this context alleviates difficult cases observed for both UHF orbitals and OOMP2 orbitals. Removing 2 multireference systems and 12 systems with ambiguous experimental data leaves a pruned data set. Overall performance on the pruned data set highlights CCSD(T) with a B97 orbital reference (CCSD(T):B97), CCSD(T) with a $κ$-OOMP2 orbital reference (CCSD(T):$κ$-OOMP2), and CCSD(T) with a B97M-rV orbital reference (CCSD(T):B97M-rV) with RMSDs of 8.48 cm$^{-1}$ and 8.50 cm$^{-1}$, and 8.75 cm$^{-1}$ respectively, outperforming CCSD(T):UHF by nearly a factor of 5. Moreover, the performance on the closed- and open-shell subsets show these methods are able to treat open-shell and closed-shell systems with comparable accuracy and robustness. The use of $κ$-OOMP2 orbitals has also proven useful in diagnosing multireference character that can hinder the reliability of CCSD(T).
