Structure factor of amorphous TiO2 nanoparticle; Molecular Dynamics Study

Three samples of amorphous TiO2 of 3 nm size are prepared by molecular dynamics simulations using different heating and quenching rates and open boundary conditions. Matsui–Akaogi force field is used to calculate the correlation functions. It is found that atomic distribution in these samples differ within the limit of 4%. The calculated coordination numbers suggest that 52–54% Ti atoms are 6-fold coordinated, 31–32% Ti atoms are 5-fold coordinated, 7–10% are 4-fold coordinated and few Ti atoms even 7-fold coordinated through vertex and edge sharing in these samples. On the other hand 66–68% oxygen atoms remain 3-fold coordinated, 25–28% are 2-fold coordinated and 5–6% oxygen atoms become 4-fold coordinated. Most of the over coordinated and under coordinated strained structures are in the core and surface regions respectively. The agreement between the calculated and measured reduced structure factors suggests that atomic arrangements in the laboratory samples prepared by sputtering and sol-gel methods may be similar to those predicted by molecular dynamics simulations.

► Three samples of amorphous TiO2 are generated using different procedures at 315K. ► Atoms are differently distributed in the core, center and surface of the 3 samples. ► Atomic distributions in the samples differ within the limit of 4%. ► Most of the over & under coordinated structures are at the core & surface resp. ► Atomic arrangement of samples prepared in lab & by MD simulations may be similar.