Ab Initio Insights into Amorphous Oxides and Short-Range Order in Quantum and Electrochemical Systems

Recent advances in atomistic modeling have improved our understanding of the critical role that disordered amorphous oxides play in both quantum computing and corrosion science. In this talk, I will present recent results from our group that link the thermochemical and electronic features of amorphous oxides to their formation pathways and underlying short-range order (SRO), to enable the rational design of materials with tailored functionalities. First, in superconducting qubits, native amorphous oxide layers formed on thin-film capacitors or resonators significantly influence coherence times. Our ab initio investigations show that Ta₂O_5-x exhibits superior performance over Nb₂O_5-x due to its reduced oxygen deficiency and enhanced Ta–Ta bonding, which suppresses magnetic moments and mitigates two-level system (TLS) formation, i.e., key sources of decoherence and noise in transmon qubits. Second, I explore the percolation theory of passivation in size-mismatched Cu–Rh alloys, where chemical short-range order (SRO) governs the formation and stability of protective oxide layers. Using cluster expansion and Monte Carlo simulations, we construct SRO and chemical percolation diagrams that predict alloy behavior under corrosive conditions. While SRO is studied here within a crystalline phase, its influence extends to the structure and properties of the resulting amorphous oxide networks post-passivation. I conclude by describing how these studies provide a unified framework where atomic-scale disorder, whether in quantum devices or corrosion-resistant alloys, can be systematically understood and engineered to improve performance.