Lu Xiya, Duchimaza-Heredia Juan, Cui Qiang
Department of Chemistry and Theoretical Chemistry Institute , University of Wisconsin-Madison , 1101 University Avenue , Madison , Wisconsin 53706 , United States.
J Phys Chem A. 2019 Aug 29;123(34):7439-7453. doi: 10.1021/acs.jpca.9b05072. Epub 2019 Aug 15.
The description of chemical bonding by the density functional tight binding (DFTB) model is analyzed using natural bonding orbitals (NBOs) and compared to results from density functional theory (B3LYP/aug-cc-pVTZ) calculations. Several molecular systems have been chosen to represent fairly diverse bonding scenarios that include standard covalent bonds, hypervalent interactions, multicenter bonds, metal-ligand interactions (with and without the pseudo-Jahn-Teller effect), and through-space donor-acceptor interactions. Overall, the results suggest that DFTB3/3OB provides physically sound descriptions for the different bonding scenarios analyzed here, as reflected by the general agreement between DFTB3 and B3LYP NBO properties, such as the nature of the NBOs, the magnitudes of natural charges and bond orders, and the dominant donor-acceptor interactions. The degree of ligand-to-metal charge transfer and the ionic nature of pentavalent phosphate are overestimated, likely reflecting the minimal-basis nature of DFTB3/3OB. Moreover, certain orbital interactions, such as geminal interactions, are observed to be grossly overestimated by DFTB3 for hypervalent phosphate and several transition metal compounds that involve copper and nickel. The study indicates that results from NBO analysis can be instructive for identifying electronic structure descriptions at the approximate quantum-mechanical level that require improvement and thus for guiding the systematic improvement of these methods.
利用自然键轨道（NBO）对密度泛函紧束缚（DFTB）模型的化学键描述进行了分析，并与密度泛函理论（B3LYP/aug-cc-pVTZ）计算结果进行了比较。选择了几个分子体系来代表相当多样的键合情况，包括标准共价键、超价相互作用、多中心键、金属-配体相互作用（有和没有赝 Jahn-Teller 效应）以及空间供体-受体相互作用。总体而言，结果表明 DFTB3/3OB 对本文分析的不同键合情况提供了合理的物理描述，这体现在 DFTB3 和 B3LYP 的 NBO 属性之间的总体一致性上，例如 NBO 的性质、自然电荷和键级的大小以及主要的供体-受体相互作用。配体到金属的电荷转移程度和五价磷酸盐的离子性质被高估了，这可能反映了 DFTB3/3OB 的最小基性质。此外，对于超价磷酸盐以及几种涉及铜和镍的过渡金属化合物，DFTB3 对某些轨道相互作用（如偕偶相互作用）的估计明显过高。该研究表明，NBO 分析的结果对于识别在近似量子力学水平上需要改进的电子结构描述具有指导意义，从而有助于指导这些方法的系统改进。
