Theoretical research for oxidation mechanism of [formula omitted]-Ti: A combination of DFT and ab initio molecular dynamics study.

Density functional theory (DFT) and ab initio molecular dynamics (AIMD) calculations are combined to study the α-Ti oxidation mechanism on atomic scale. The most and second stable adsorption site for O atoms on the surface layer is FCC and HCP site, respectively. The most stable adsorption site of subsurface layer is octahedral site. O atoms all gain electrons from adsorbed Ti atoms and the Ti–O bonds are mainly formed by the hybridization between O-p and Ti-d orbitals. At both 303 K and 873 K, AIMD results show that O 2 molecule gradually dissociate into O atoms on α-Ti (0001) surface and then adsorb on the surface. The increase of temperature accelerates the dissociation rate of O 2 molecule. During the formation of Ti–O bond, O and Ti atom gain and lose electrons, respectively. The partial density of states evolution results show that the Ti–O bond is formed by the gradually strengthened hybridization between O-p and Ti-d orbitals. At 303 K, α-Ti (0001) surface can form a dense oxide film. But a discontinuous and loose oxide film is formed at 873 K and O atoms can penetrate into the octahedral and tetrahedral sites of the subsurface layer. • DFT and AIMD were combined to reveal the α-Ti oxidation mechanism. • Adsorption behavior of O atom on surface and subsurface was studied by DFT. • The dynamic dissociation and adsorption process of O 2 was investigated by AIMD. • The temperature effect on the O 2 dissociation behavior was studied by AIMD. • Electronic structure during DFT and AIMD calculation were investigated. [ABSTRACT FROM AUTHOR]