Structural stability and thermodynamic properties of (La2O3)n (n = 1–7) clusters system based on density functional theory

Abstract

The initial configurations of nano‑lanthanum oxide clusters (La₂O₃)_n (n = 1–7) were constructed using a combination of the artificial bee colony algorithm and density functional theory. For the first time, the medium-sized cluster structure with seven lanthanum oxide molecules was established. By optimizing different structures and calculating the vibration frequency, many new configurations different from previous studies were obtained. The average binding energy, second-order difference energy, HOMO-LUMO energy gap, density of states, and molecular orbital properties of the cluster system were analyzed. On this basis, the thermodynamic properties and behavior of nano‑lanthanum oxide clusters under different temperature and molecular number conditions were discussed. The results show that with an increase in the number of molecules, the cluster structure gradually changes from cage-like to spatial ladder-like, and finally to ellipsoid-like. The nanoclusters are stable overall, with relatively higher stability when n = 2,4, and the effect of the lanthanum oxygen atomic orbital on the molecular orbital of the cluster is analyzed. The Cv, Cp, S, and H of (La₂O₃)_n (n = 1–7) clusters increase with temperature, and increase with the number of molecules, while G and Gv decrease with temperature, with changes in the number of molecules greatly affected by E (0 K) and T. The thermodynamic properties of lanthanum oxide clusters with larger molecular numbers are more sensitive to temperature changes. The results provide a theoretical basis for the evolution mechanism of lanthanum oxide clusters-crystals and valuable information for further study of the growth law of rare earth oxide molecular clusters.