Department of Chemistry, Memorial University, St. John's, Newfoundland, Canada A1B 3X7.
J Chem Theory Comput. 2008 Jan;4(1):86-100. doi: 10.1021/ct700224j.
Ab initio calculations were carried out for isogyric reactions involving the third row elements, Ga, Ge, As, Se, and Br. Geometries of all the reactants and products were optimized at the HF, MP2, and B3LYP levels of theory using the 6-31G(d) and 6-31G(d,p) basis sets. For molecules containing third row elements geometries, frequencies and thermodynamic properties were calculated using both the standard 6-31G and the Binning-Curtiss (BC6-31G) basis sets. In order to determine the performance of these basis sets, the calculated thermodynamic properties were compared to G3MP2 values and where possible to experimental values. Geometries and frequencies calculated with the standard 6-31G and the BC6-31G basis sets were found to differ significantly. Frequencies calculated with the standard 6-31G basis set were generally in better agreement with the experimental values (MAD=40.1 cm(-1) at B3LYP/6-31G(d,p) and 94.2 cm(-1) at MP2/6-31G(d,p) for unscaled frequencies and 29.6 cm(-1) and 24.4 cm(-1), respectively, for scaled frequencies). For all the reactions investigated, the thermodynamic properties calculated with the standard 6-31G basis set were found to consistently be in better agreement with the G3MP2 and the available experimental results. However, the BC6-31G basis set performs poorly for the reactions involving both second and third row elements. Since, in general, the standard 6-31G basis set performs well for all the reactions, we recommend that the standard 6-31G basis set be used for calculations involving third row elements. Using G3MP2 enthalpies of reaction and available experimental heats of formation (ΔHf), previously unknown ΔHf for CH3SeH, SiH3SeH, CH3AsH2, SiH3AsH2, CH3GeH3, and SiH3GeH3 were found to be 18.3, 18.0, 38.4, 82.4, 41.9, and 117.4 kJ mol(-1), respectively.
从头计算方法被应用于包含第三周期元素镓、锗、砷、硒和溴的等电子反应。所有反应物和产物的几何构型都是在 HF、MP2 和 B3LYP 理论水平下，采用 6-31G(d)和 6-31G(d,p)基组优化得到的。对于含有第三周期元素的分子，使用标准的 6-31G 和 Binning-Curtiss（BC6-31G）基组来计算频率和热力学性质。为了确定这些基组的性能，将计算得到的热力学性质与 G3MP2 值进行了比较，在可能的情况下，还与实验值进行了比较。发现标准 6-31G 和 BC6-31G 基组计算得到的几何构型和频率有显著差异。使用标准 6-31G 基组计算得到的频率通常与实验值更为吻合（未经缩放的频率在 B3LYP/6-31G(d,p)下为 40.1 cm(-1)，在 MP2/6-31G(d,p)下为 94.2 cm(-1)，而经缩放的频率分别为 29.6 cm(-1)和 24.4 cm(-1)）。对于所有研究的反应，使用标准 6-31G 基组计算得到的热力学性质与 G3MP2 和可用的实验结果更为一致。然而，BC6-31G 基组对于涉及第二和第三周期元素的反应表现不佳。由于一般来说，标准 6-31G 基组对于所有反应都能很好地工作，因此我们建议在涉及第三周期元素的计算中使用标准 6-31G 基组。使用 G3MP2 反应焓和可用的实验生成焓（ΔHf），我们发现 CH3SeH、SiH3SeH、CH3AsH2、SiH3AsH2、CH3GeH3 和 SiH3GeH3 的未知 ΔHf 值分别为 18.3、18.0、38.4、82.4、41.9 和 117.4 kJ mol(-1)。
