Bickelhaupt F Matthias, Solà Miquel, Guerra Célia Fonseca
Afdeling Theoretische Chemie, Scheikundig Laboratorium der Vrije Universiteit, De Boelelaan 1083, NL-1081 HV Amsterdam, The Netherlands.
Inorg Chem. 2007 Jun 25;46(13):5411-8. doi: 10.1021/ic070328u. Epub 2007 Jun 1.
We have investigated table salt and other alkali metal chloride monomers, ClM, and (distorted) cubic tetramers, (ClM)(4), with M = Li, Na, K, and Rb, using density functional theory (DFT) at the BP86/TZ2P level. Our objectives are to determine how the structure and thermochemistry (e.g., Cl-M bond lengths and strengths, oligomerization energies, etc.) of alkali metal chlorides depend on the metal atom and to understand the emerging trends in terms of quantitative Kohn-Sham molecular orbital (KS-MO) theory. The analyses confirm the high polarity of the Cl-M bond (dipole moment, VDD, and Hirshfeld atomic charges). They also reveal that bond overlap derived stabilization (approximately -26, -20, and -8 kcal/mol), although clearly larger than in the corresponding F-M bonds, contributes relatively little to the (trend in) bond strengths (-105, -90, and -94 kcal/mol) along M = Li, Na, and K. Thus, the Cl-M bonding mechanism resembles more closely that of the even more ionic F-M bond than that of the more covalent C-M or H-M bonds. Tetramerization causes the Cl-M bond to expand, and it reduces its polarity.
我们使用BP86/TZ2P水平的密度泛函理论（DFT）研究了食盐及其他碱金属氯化物单体ClM和（畸变的）立方四聚体(ClM)₄，其中M = Li、Na、K和Rb。我们的目标是确定碱金属氯化物的结构和热化学性质（例如，Cl-M键长和键能、齐聚化能等）如何依赖于金属原子，并根据定量的Kohn-Sham分子轨道（KS-MO）理论理解其呈现出的趋势。分析证实了Cl-M键的高极性（偶极矩、VDD和Hirshfeld原子电荷）。分析还表明，尽管键重叠衍生的稳定性（约为-26、-20和-8 kcal/mol）明显大于相应的F-M键，但对沿M = Li、Na和K的（键能趋势）贡献相对较小（-105、-90和-94 kcal/mol）。因此，Cl-M键合机制更类似于离子性更强的F-M键，而不是共价性更强的C-M或H-M键。四聚化导致Cl-M键伸长，并降低其极性。
