Polishing the Gold Standard: The Role of Orbital Choice in CCSD(T) Vibrational Frequency Prediction

Abstract

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 ($\kappa$-OOMP2) orbitals as reference orbitals for MP3, we investigate the use of $\kappa$-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 $\kappa$-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 $\kappa$-OOMP2 orbital reference (CCSD(T):$\kappa$-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 $\kappa$-OOMP2 orbitals has also proven useful in diagnosing multireference character that can hinder the reliability of CCSD(T).

References in corpus (5)

• Eliminating spin contamination in auxiliary-field quantum Monte Carlo: realistic potential energy curve of F2
• Distinguishing Artificial and Essential Symmetry Breaking in a Single Determinant: Approach and Application to the C${}_{60}$, C${}_{36}$, and C${}_{20}$ Fullerenes
• Two Single-Reference Approaches to Singlet Biradicaloid Problems: Complex, Restricted Orbitals and Approximate Spin-Projection Combined With Regularized Orbital-Optimized Møller-Plesset Perturbation Theory
• Utilizing Essential Symmetry Breaking in Auxiliary-Field Quantum Monte Carlo: Application to the Spin Gaps of the C${}_{36}$ Fullerene and an Iron Porphyrin Model Complex
• Third order Møller-Plesset theory made more useful? The role of density functional theory orbitals

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• Hierarchical quantum embedding by machine learning for large molecular assemblies
• Elucidating the molecular orbital dependence of the total electronic energy in multireference problems
• Accurate harmonic vibrational frequencies for diatomic molecules via quantum computing