S. Ogata et al., Role of atomic charge transfer on sintering of TiO2 nanoparticles: Variable-charge molecular dynamics, J APPL PHYS, 88(10), 2000, pp. 6011-6015
The stability of surface structure and space-charge distribution in free Ti
O2 nanoparticles are investigated for both rutile and anatase phases using
a variable-charge interaction potential in which atomic charges vary dynami
cally depending on their environment. We find the dynamic charge transfer:
(i) enhances atomic diffusion at surfaces of the spherical nanoparticles at
high temperatures; and (ii) creates additional repulsive force between the
two nanospheres through formation of a double-charge surface layer in each
nanosphere. The surface diffusion due to the charge transfer clearly disti
nguishes the two nanospheres with different underlying crystalline structur
es; the surface diffusion constant of the anatase sphere is almost three ti
mes as great as that of the rutile sphere. Variable-charge molecular dynami
cs simulations are then applied to sintering of two TiO2 nanospheres. It tu
rns out that the enhanced surface diffusion in the anatase nanosphere at hi
gh temperatures significantly promotes neck formation between the two spher
es. (C) 2000 American Institute of Physics. [S0021-8979(00)08323-7].