Insight into the stability in cation substitution of Magnéli phase Ti4O7.

Doping Magnéli phase Ti₄O₇ by cation substitution has attracted some interest for modulating structure and properties enhancement, but it remains a big problem to understand how doping elements impact the thermodynamic and structural stability of Ti₄O₇. We utilized first-principles calculations based on density functional theory (DFT) combined with machine learning (ML) to forecast the stability of doped Ti₄O₇. DFT calculations are used to model the thermodynamic and structural stability, as well as the electronic structure, of doped (Ti,M)₄O₇ complexes (M = Sc, Y, La, Ce, Zr, Hf, V, Nb, Ta, Cr, Mo, and W). The results reveal that even if all (Ti,M)₄O₇ are thermodynamically stable, the introduction of rare earth elements Y, La, and Ce causes great structural distortion. Employing Zr, Nb, Mo, and W can improve Ti₄O₇ thermodynamic stability due to strong bond strength and minimal lattice distortion. The relevance of 78 doping element qualities and one processing feature (doping site) for (Ti,M)₄O₇ stability is discovered using ML. The results show that modulus of rigidity and entropy of solid of doping atoms have the greatest influence on the thermodynamic and structural stability of doped Ti₄O₇, which is useful for predicting additional (Ti,M)₄O₇ stability without DFT calculations. At a low doping concentration, Ce-doped Ti₄O₇ with massive lattice distortion was synthesized, supporting the DFT results. This study not only applies to all doped Ti₄O₇ complexes, setting the groundwork for stability of the planned high-performance cation substitution in defect Ti₄O₇, but also introduces a unique way of predicting stability in defect engineering. [ABSTRACT FROM AUTHOR]