2019 年 62 巻 8 号 p. 486-491
The divide-and-conquer type density functional tight-binding molecular dynamics (DC-DFTB-MD) is a useful method to simulate chemical reactions of large systems. The present study applied the method to surface reaction, namely, proton diffusion process between H2O and OH on Pt(111) surface. The proton diffusion coefficients for systems with different surface coverage, ratio of adsorbed molecules, and temperature were estimated. The calculated results showed that the proton diffusion process in six-membered ring hydrogen bond network is an order of magnitude slower than that in no-six-membered ring structures. Furthermore, we confirmed the elevation of temperature from typical experimental condition of 130 K leads to more frequent proton transfer events and larger proton diffusion coefficients, while the magnitude of increasing trend varies between with and without the six-membered ring structure. The present study indicated that the proton diffusion process strongly depends on the local structure of H2O and OH layer at Pt(111) surface.