Bende David, Grin Yuri, Wagner Frank R
Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer Strasse 40, 01187 Dresden (Germany), Fax: (+49) 351-4646-4002.
Chemistry. 2014 Jul 28;20(31):9702-8. doi: 10.1002/chem.201400299. Epub 2014 Jul 2.
MgAgAs-type "half-Heusler" compounds are known to realize two out of three possible atomic arrangements of this structure type. The number of transition metal components typically determines which of the alternatives is favored. On the basis of DFT calculations for all three variants of 20 eight- and eighteen-valence-electron compounds, the experimentally observed structural variant was found to be determined by basically two different bonding patterns. They are quantified by employing two complementary position-space bonding measures. The Madelung energy E((M)(QTAIM)) calculated with the QTAIM effective charges reflects contributions of the ionic interactions to the total energy. The sum of nearest-neighbor delocalization indices ςnn characterizes the covalent interactions through electron sharing. With the aid of these quantities, the energetic sequence of the three atomic arrangements for each compound is rationalized. The resulting systematic is used to predict a scenario in which an untypical atomic arrangement becomes most favorable.
已知MgAgAs型“半赫斯勒”化合物实现了这种结构类型三种可能原子排列中的两种。过渡金属组分的数量通常决定了哪种排列更受青睐。基于对20种八价和十八价电子化合物的所有三种变体的密度泛函理论（DFT）计算，发现实验观察到的结构变体基本上由两种不同的键合模式决定。通过采用两种互补的位置空间键合度量对它们进行量化。用QTAIM有效电荷计算的马德隆能量E((M)(QTAIM))反映了离子相互作用对总能量的贡献。最近邻离域指数ςnn的总和通过电子共享表征共价相互作用。借助这些量，合理化了每种化合物的三种原子排列的能量顺序。由此产生的系统性用于预测一种非典型原子排列变得最有利的情况。
