Unusual electronic and bonding properties of the Zintl phase Ca5Ge3 and related compounds. A theoretical analysis

Anja-Verena Mudring; John D Corbett

doi:10.1021/ja030216b

Unusual electronic and bonding properties of the Zintl phase Ca5Ge3 and related compounds. A theoretical analysis

J Am Chem Soc. 2004 Apr 28;126(16):5277-81. doi: 10.1021/ja030216b.

Authors

Anja-Verena Mudring¹, John D Corbett

Affiliation

¹ Ames Laboratory and Department of Chemistry, Iowa State University, Ames, Iowa 50011 USA.

PMID: 15099112
DOI: 10.1021/ja030216b

Abstract

Theoretical reasons for metallic behavior among diverse Zintl phases have generally not been pursued at an advanced level. Here, the electronic structure of Ca5Ge3 (Cr5B3 type), which can be formulated (Ca+2)5(Ge2-6)Ge-4 in oxidation states, has been explored comparatively by means of semiempirical and first-principles density functional methods. The FP-APW calculations show that alkaline-earth-metal and germanium orbitals, particularly the d orbitals on the cations and the p-pi orbitals of the halogen-like dimeric Ge2-6, mix considerably to form a conduction band. This covalency perfectly explains the unusual metallic properties of the nominally electron-precise Zintl phase Ca5Ge3 and its numerous relatives. Similar calculational results are obtained for Sr5Ge3, Ba5Ge3, and Ca5Sn3. Cation d orbitals appear to be a common theme among Zintl phases that are also metallic.