Sr2Pd4Al5: Synthesis, Crystal and Electronic Structures, and Chemical Bonding of a Polar Intermetallic Compound

Abstract

AbstractThe new intermetallic compound Sr2Pd4Al5 was prepared from the elements by reaction in niobium ampoules. The structure was refined from single‐crystal data, which indicate the formation of a new structure type in the orthorhombic crystal system [a = 1814.49(10), b = 431.64(4), c = 1102.47(4) pm] with space group Pnma (wR2 = 0.0251, 1666 F2 values, 68 parameters). Full ordering of the transition‐metal and aluminum sites was observed. The compound can be described as a polar intermetallic phase with a polyanionic [Pd4Al5]δ– network; however, a quite unique bonding situation was found within this framework. In addition to the usual Pd–Al bonding, significant contributions to the stability of the framework caused by homoatomic Pd–Pd and Al–Al interactions can also be found. Structural relaxation confirmed the electronic stability and predicted the compound to be a metallic conductor.