Department of Chemistry, Iowa State University, Ames, Iowa 50011, USA.
Inorg Chem. 2011 Aug 15;50(16):7625-36. doi: 10.1021/ic200643f. Epub 2011 Jul 20.
To enhance understanding of the Zintl-Klemm concept, which is useful for characterizing chemical bonding in semimetallic and semiconducting valence compounds, and to more effectively rationalize the structures of Zintl phases, we present a partitioning scheme of the total energy calculated on numerous possible structures of the alkali metal trielides, LiAl, LiTl, NaTl, and KTl, using first-principles quantum mechanical calculations. This assessment of the total energy considers the relative effects of covalent, ionic, and metallic interactions, all of which are important to understand the complete structural behavior of Zintl phases. In particular, valence electron transfer and anisotropic covalent interactions, explicitly employed by the Zintl-Klemm concept, are often in competition with isotropic, volume-dependent metallic and ionic interaction terms. Furthermore, factors including relativistic effects, electronegativity differences, and atomic size ratios between the alkali metal and triel atoms can affect the competition by enhancing or weakening one of the three energetic contributors and thus cause structural variations. This partitioning of the total energy, coupled with analysis of the electronic density of states curves, correctly predicts and rationalizes the structures of LiAl, LiTl, NaTl, and KTl, as well as identifies a pressure-induced phase transition in KTl from its structure, based on Tl(6) distorted octahedra, to the double diamond NaTl-type.
为了增强对 Zintl-Klemm 概念的理解，该概念对于描述类金属和半导体价化合物中的化学成键很有用，并更有效地合理化 Zintl 相的结构，我们提出了一种分区方案，用于划分碱金属 trielide（LiAl、LiTl、NaTl 和 KTl）的许多可能结构的总能量的计算，使用第一性原理量子力学计算。这种总能量的评估考虑了共价、离子和金属相互作用的相对影响，所有这些对于理解 Zintl 相的完整结构行为都很重要。特别是，价电子转移和各向异性共价相互作用（Zintl-Klemm 概念中明确采用的）通常与各向同性、体积依赖性的金属和离子相互作用项竞争。此外，包括相对论效应、电负性差异以及碱金属和 triel 原子之间的原子大小比在内的因素会通过增强或削弱三个能量贡献者之一来影响竞争，从而导致结构变化。这种总能量的分区，加上对电子态密度曲线的分析，正确地预测和合理化了 LiAl、LiTl、NaTl 和 KTl 的结构，并根据Tl(6)扭曲八面体识别出 KTl 在压力下从其结构到双金刚石 NaTl 型的相变。
