Unveiling the electronic structures and ligation effect of the superatom–polymeric zirconium oxide clusters: a computational study

Abstract

Discovering the non-noble ZrO cluster as an analog of the noble metal catalyst Pd is of significance toward designing functional materials with fine-tuned properties using the superatom concept. The effect of gradually assembling the ZrO superatomic unit on the electronic structures and chemical bonding of larger ZrO–polymeric clusters, however, is unclear. Herein, by using density functional theory (DFT) calculations, the lowest-energy structures and low-lying isomers of the (ZrO)_n^−/0 (n = 2–5) clusters were optimized, in which every O atom in these clusters tends to connect its adjacent two Zr atoms forming metal oxygen bridge bonds. Insights into the electronic characteristics of these clusters were obtained by analyzing their molecular orbitals (MOs) and density of states (DOS). More importantly, our studies on the CO (electron acceptor) and PH₃ (electron donor) ligated Zr₃O₃ clusters unveil that the ligation process can substantially alter the electronic properties of the clusters by tuning the HOMO and LUMO states, which may have potential applications in photovoltaics. Strikingly, the successive attachment of PH₃ on Zr₃O₃ dramatically lowers the adiabatic ionization potential (AIP) of the ligated clusters, resulting in the formation of stable superalkali clusters with large HOMO–LUMO gaps. Furthermore, the potential of constructing the superalkali Zr₃O₃(PH₃)₅ based 1-D cluster assembled material was also examined.