Gladfelter Wayne L, Cramer Christopher J
Department of Chemistry, University of Minnesota 207 Pleasant St., SE Minneapolis MN 55455 USA
Department of Chemistry, Chemical Theory Center, Minnesota Supercomputing Institute, University of Minnesota 207 Pleasant St., SE Minneapolis MN 55455 USA.
RSC Adv. 2019 Sep 17;9(50):29448-29455. doi: 10.1039/c9ra07144j. eCollection 2019 Sep 13.
The lattice energies of [HGaNH], [HBNH] and [HGeCH] in their experimentally determined space groups, 2/, 2 and , respectively, were calculated using density functional methods for periodic structures with the periodic code CRYSTAL17. Using the basis set pob-TZVP for all calculations, B3LYP including Grimme's D3 dispersion correction was found to reproduce experimental bond distances and angles most accurately. CRYSTAL17 was also used to optimize geometries and calculate energies of the molecular structures in the gas phase. While the chair conformation of the six-membered rings is found in all of the crystals, only [HGeCH] retains this as the preferred conformation in the gas phase. By contrast, a twist-boat conformation is preferred for both [HGaNH] and [HBNH] in the gas phase, and thus a correction for this change in conformation must be included in corresponding sublimation enthalpy calculations. In addition to the D3 dispersion correction, all lattice energies included a correction for basis set superposition error. The lattice energies for [HGaNH], [HBNH] and [HGeCH] were 153.5, 120.8 and 84.9 kJ mol, respectively. These values were used to calculate the sublimation enthalpies, which exhibited good agreement for the single case where an experimental measurement is available, namely [HBNH] (exp Δ (298), 119 ± 12 kJ mol; calcd, 119.4 kJ mol). The energetic impact of the crystal structure was assessed by minimizing the structures of each molecule in each of the three space groups spanned by them experimentally and calculating their respective lattice energies. In every case, the experimentally observed space group was the one computed to be the most stable.
采用密度泛函方法，借助周期代码CRYSTAL17，分别计算了实验测定的空间群2/、2和 中[HGaNH]、[HBNH]和[HGeCH]的晶格能。所有计算均使用基组pob-TZVP，发现包含Grimme的D3色散校正的B3LYP能最准确地再现实验键长和键角。CRYSTAL17还用于优化气相中分子结构的几何构型并计算其能量。虽然在所有晶体中都发现了六元环的椅式构象，但只有[HGeCH]在气相中保持这种构象作为优选构象。相比之下，[HGaNH]和[HBNH]在气相中更倾向于扭曲船式构象，因此在相应的升华焓计算中必须考虑这种构象变化的校正。除了D3色散校正外，所有晶格能都包含对基组叠加误差的校正。[HGaNH]、[HBNH]和[HGeCH]的晶格能分别为153.5、120.8和84.9 kJ/mol。这些值用于计算升华焓，对于有实验测量值的单一情况，即[HBNH]（实验值Δ(298)，119±12 kJ/mol；计算值，119.4 kJ/mol），结果显示出良好的一致性。通过对每个分子在它们实验所跨越的三个空间群中的结构进行最小化，并计算它们各自的晶格能，评估了晶体结构的能量影响。在每种情况下，实验观察到的空间群都是计算得出的最稳定的空间群。
