Abstract:

In this paper, we develop a surface atom identification model to perform atom identification and analysis of the surface atoms of a single TiO₂ nanoparticle during the heating and sintering process. Cubic mesh was used to obtain the particle structure mesh, and the optimal mesh size of 0.3 nm was determined by volumetric integration of a spherical particle. Surface atoms were classified according to identification of surface meshes, and the number of external meshes in all of the neighbor meshes (N_ext) was set as a criterion to determine whether the target mesh was a surface mesh. The optimal value was N_ext=9. LAMMPS was used to simulate the heating process of a particle with a radius of 0.75 nm. The results show that energy relaxation is significantly faster than structure relaxation. The atom classification analysis with the developed surface atom identification model shows that displacement of the surface atoms is larger than the interior atoms, and surface O atoms are more active in migration than surface Ti atoms. The coordination number of surface atoms is lower than that of interior atoms. The present study provides fundamental information for analyzing the active structure distribution of nanoparticles.

Key words: TiO₂, Nanoparticle, Molecular dynamics, Surface identification, Surface atom