First-principles calculations on LaAlO3 as the heterogeneous nucleus of austenite

Abstract

In this work, the interface atomic structure, bonding character, adhesion work and interfacial energy of LaAlO3 (100)/austenite (100) interface were studied and the effectiveness of the LaAlO3 as the heterogeneous nucleus of austenite was analyzed by first-principles calculations. The results indicate that, in LaAlO3 bulk, the charge transfer and sp2 orbital hybridization not only appear between La atom and O atom, but also between Al atom and O atom, which indicate that the chemical bond in LaAlO3 bulk is a mixed one with both covalent and ionic characteristics. For LaAlO3 (100) surface, when La chemical potential (ΔμLa) is low, AlO2 terminated structure is stable than LaO terminated one. However, when La chemical potential (ΔμLa) is high, LaO terminated structure is stable than AlO2 terminated one. For austenite (100) surface, doped C terminated structure is stable than lack C terminated one all along. In the four LaAlO3 (100)/austenite (100) interfaces, the LaO-doped C terminated structure has the largest adhesion work and the smallest interface distance, which indicate that it is the most stable. The effectiveness of LaAlO3 as the heterogeneous nucleus of austenite is related with ΔμLa and ΔμC. When ΔμLa is low, the LaAlO3 (100)/austenite (100) interface with AlO2 terminated structure meets the energy requirements as the heterogeneous nucleation interface. With the increase of ΔμLa, the LaAlO3 (100)/austenite (100) interface with AlO2 terminated structure cannot be the LaAlO3/austenite heterogeneous nucleation interface any longer, while that with LaO terminated structure, especially with LaO-doped C terminated structure, meets the energy requirements as the heterogeneous nucleation interface greatly.