Di Grande Silvia, Lazzari Federico, Barone Vincenzo
Scuola Normale Superiore di Pisa, Piazza dei Cavalieri 7, 56126 Pisa, Italy.
Scuola Superiore Meridionale, Largo San Marcellino 10, 80138 Napoli, Italy.
J Chem Theory Comput. 2024 Oct 22;20(20):9243-9258. doi: 10.1021/acs.jctc.4c00900. Epub 2024 Oct 7.
Accurate geometries of small semirigid molecules in the gas phase are available thanks to high-resolution spectroscopy and accurate quantum chemical approaches. These results can be employed for validating cheaper low-level quantum chemical models or correcting the corresponding structures of large molecules. On these grounds, in this work, a large panel of semiexperimental equilibrium structures already available in the literature is used to confirm the average error (1 mÅ for bond lengths and 2 mrad for valence angles) of a version of the Pisa composite schemes (PCS2), which is applicable to molecules containing up to about 20 atoms. Then, the geometries of 30 additional medium-sized systems were optimized at the PCS2 level to cover a more balanced chemical space containing moieties poorly represented in SE compilations. The final database is available on a public domain Web site (https://www.skies-village.it/databases/) and can be employed for correcting structures of larger molecules obtained by hybrid or double-hybrid density functionals in the framework of the templating molecule approach. Several examples show that corrections based on the structures of building blocks taken from this database reduce the error of the B3LYP geometrical parameters of large molecules by nearly an order of magnitude without increasing the computational cost. Furthermore, the results of different density functional theory (DFT) or wave function (e.g., MP2) models can be improved in the same way by simply computing both the whole molecule and suitable building blocks at the chosen level. Then, whenever reference structures of some building blocks containing up to about 20 atoms are not available, they can be purposely optimized at the PCS2 level by employing reasonable computer resources. Therefore, a new DFT-cost tool is now available for the accurate characterization of large molecules by experiment-oriented scientists.
借助高分辨率光谱学和精确的量子化学方法，可以获得气相中小的半刚性分子的精确几何结构。这些结果可用于验证成本较低的低水平量子化学模型或校正大分子的相应结构。基于这些理由，在本工作中，使用文献中已有的大量半实验平衡结构来确认比萨复合方案（PCS2）一个版本的平均误差（键长为1 mÅ，价角为2 mrad），该版本适用于包含约20个原子的分子。然后，在PCS2水平上对另外30个中等大小的体系进行几何结构优化，以涵盖一个更平衡的化学空间，该空间包含在半实验汇编中代表性不足的部分。最终数据库可在公共网站（https://www.skies-village.it/databases/）上获取，并可用于在模板分子方法框架内校正通过杂化或双杂化密度泛函获得的大分子结构。几个例子表明，基于从该数据库中获取的构建块结构进行的校正，可将大分子B3LYP几何参数的误差降低近一个数量级，而不会增加计算成本。此外，通过在选定水平上简单地计算整个分子和合适的构建块，不同密度泛函理论（DFT）或波函数（如MP2）模型的结果也可以以同样的方式得到改进。然后，每当一些包含约20个原子的构建块的参考结构不可用时，可以通过合理利用计算机资源在PCS2水平上对其进行专门优化。因此，一种新的DFT成本工具现在可供以实验为导向的科学家用于精确表征大分子。
