K<sub>2</sub>BaSi<sub>4</sub>: Zintl Concept in Position Space
Olga Sichevych, Lev Akselrud, Bodo Böhme, Matej Bobnar, Michael Baitinger, Frank R. Wagner, Yuri Grin
Abstract
Abstract The Zintl phase K 2 BaSi 4 has been synthesized from the mixture of precursors KSi and BaSi 2 . The crystal structure of K 2 BaSi 4 was elucidated from X‐ray powder diffraction data: Pearson symbol oP 28, space group Pbcm , a =9.4950(1), b =9.2392(1), c =9.9025(1) Å. The main building block of the crystal structure are tetrahedral anions Si 4 4– . Analysis of chemical bonding for K 2 BaSi 4 and its chemical analogs – molecular H 4 Si 4 and solid state K 4 Si 4 employing the electron localizability approach reveals the basic agreement with the Zintl model in terms of number of basins for Si−Si bonds and lone pairs at Si atoms, as well as the charge transfer direction. The populations of the bond and ‘lone‐pair’ basins agree with the Zintl count for molecular species and deviate strongly for the solids, in particular, while the ‘lone‐pair’ basins are over‐populated, the bond basins are essentially under‐populated. The topology of the calculated electron density and electron‐localizability indicator is very sensitive toward the interatomic distances and angles in the Si 4 4− anion.