Atomic-Scale Origin of Facet- and Fuel-Dependent Interfacial Evolution in Al/Mg-CuO Nanothermites

Understanding atomic-scale interactions at metal/oxide interfaces is crucial for tailoring the reactivity and stability of nanothermite. In this work, density functional theory (DFT) and ab initio molecular dynamics (AIMD) were employed to investigate the initial deposition, displacement mechanisms, and coverage effects of Mg and Al on CuO(111) and CuO(1̅11) surfaces. The results show that the two CuO surfaces exhibit similar surface composition and magnetic ordering, but CuO(111) is thermodynamically more stable due to its bulk-like charge distribution, smaller geometric distortion, and more dispersed surface states. Adsorption analyses reveal that the less stable CuO(1̅11) exhibits stronger binding toward Mg and Al, whereas the more stable (111) surface shows greater Cu_3c reduction and Cu-O bond activation, indicating a decoupling between surface stability and interfacial chemical reactivity. Fuel-dependent analysis further indicates that Mg promotes electron transfer to Cu_3c through more ionic Mg-O bonding, while more covalent Al-O bonding more effectively weakens adjacent Cu_3c-O_3c bonds. AIMD and reaction path searches demonstrate that Cu displacement readily occurs on CuO(111) at low coverage, with Mg being kinetically more favorable and Al being thermodynamically more favorable. Increasing coverage induces strong multiatom cooperativity, driving oxygen extraction and interfacial reconstruction to form highly under-coordinated amorphous oxides that remain chemically active. Overall, this study elucidates the early evolution mechanisms of Al/Mg-CuO interfaces and provides atomic-level insights into the structural design and preignition control of nanoenergetic films.