The difficulty of quantum chemically computing vibrational, rotational, and rovibrational reference data via quartic force fields (QFFs) for molecules containing aluminum appears to be alleviated herein using a hybrid approach based upon CCSD(T)‐F12b/cc‐pCVTZ further corrected for conventional CCSD(T) scalar relativity within the harmonic terms and simple CCSD(T)‐F12b/cc‐pVTZ for the cubic and quartic terms: the F12‐TcCR+TZ QFF. Aluminum containing molecules are theorized to participate in significant chemical processes in both the Earth's upper atmosphere as well as within circumstellar and interstellar media. However, experimental data for the identification of these molecules are limited, showcasing the potential for quantum chemistry to contribute significant amounts of spectral reference data. Unfortunately, current methods for the computation of rovibrational spectral data have been shown previously to exhibit large errors for aluminum‐containing molecules. In this work, ten different methods are benchmarked to determine a method to produce experimentally‐accurate rovibrational data for theorized aluminum species. Of the benchmarked methods, the explicitly correlated, hybrid F12‐TcCR+TZ QFF consistently produces the most accurate results compared to both gas‐phase and Ar‐matrix experimental data. This method combines the accuracy of the composite F12‐TcCR energies along with the numerical stability of non‐composite anharmonic terms where the non‐rigid nature of aluminum bonding can be sufficiently treated.

中文翻译：

---

计算准确且可靠的含铝分子的振动光谱数据


通过四次力场 （QFF） 对含铝分子进行量子化学计算振动、旋转和振动参考数据的困难似乎在这里得到了缓解，该方法使用基于 CCSD（T）‐F12b/cc‐pCVTZ 的混合方法进一步校正了谐波项内的常规 CCSD（T）标量相对性，并针对三次项和四次项进行了简单的 CCSD（T）‐F12b/cc‐pVTZ 校正： F12‐TcCR+TZ QFF。理论上，含铝分子参与地球高层大气以及星际和星际介质中的重要化学过程。然而，用于鉴定这些分子的实验数据是有限的，这表明量子化学有可能贡献大量的光谱参考数据。不幸的是，目前计算 rovibrational 光谱数据的方法之前已经表明，对于含铝分子来说，误差很大。在这项工作中，对 10 种不同的方法进行了基准测试，以确定一种为理论化铝种类生成实验准确的 rovibrational 数据的方法。在基准方法中，与气相和 Ar 基体实验数据相比，明确相关的混合 F12-TcCR+TZ QFF 始终产生最准确的结果。该方法结合了复合 F12-TcCR 能量的准确性和非复合非谐波项的数值稳定性，其中铝键合的非刚性性质可以得到充分处理。