(218d) Molecular Behavior of Water Confined in TiO2 Nano-Slits Using Classical, Reactive and Ab Initio Molecular Dynamics

Titanium dioxide (TiO₂) has drawn great attention from scientists and engineers in the past decade because it is expected to play an important role in helping solve many serious environmental and pollution challenges. Essentially all applications of TiO₂ involve contact between water or aqueous solution and TiO₂ surfaces. Mineral-aqueous electrolyte solution interfaces are of common occurrence in natural and industrial environments. In the interfacial region, the solution properties and the crystal structure both deviate from the characteristics of the bulk phases, and an electrical double layer (EDL) is formed in the interfacial region by absorption of ionic species and countercharges from the aqueous solution in the vicinity of the interface. The EDL exerts a profound influence on the stability and transport properties of colloids, the mobilities of trace elements in aqueous solutions in contact with solid phases, nutrient bioavailability and bacterial attachment, corrosion, crystal nucleation and growth, as well as abundant natural and industrial processes. Thus, for many applications, it is necessary to understand the dynamics of water and electrolytes in this interfacial region.

Since the dynamics of water and electrolytes confined in nanopores are very different from bulk, these dynamic properties need to be investigated directly. Molecular dynamics (MD) simulations have been used to observe the dynamics of fluid confined in nanopores. Our previous work^1-5, using classical MD simulation, could not describe reactions in the interfacial region. In this work, we report MD simulations using a reactive force field (ReaxFF) and ab initio MD (CPMD) to compare with our previous work, with the goal of obtaining more accurate dynamics for water confined in nano-slit pores, and to understand the role of bond vibration and bond breaking (reactivity) in the dynamics.

References:

         (1)    Předota, M.; Bandura, A. V.; Cummings, P. T.; Kubicki, J. D.; Wesolowski, D. J.; Chialvo, A. A.; Machesky, M. L. The Journal of Physical Chemistry B 2004, 108, 12049.

         (2)    Mamontov, E.; Vlcek, L.; Wesolowski, D. J.; Cummings, P. T.; Wang, W.; Anovitz, L. M.; Rosenqvist, J.; Brown, C. M.; Garcia Sakai, V. The Journal of Physical Chemistry C 2007, 111, 4328.

         (3)    Mamontov, E.; Wesolowski, D. J.; Vlcek, L.; Cummings, P. T.; Rosenqvist, J.; Wang, W.; Cole, D. R. The Journal of Physical Chemistry C 2008, 112, 12334.

         (4)    Mamontov, E.; Vlcek, L.; Wesolowski, D. J.; Cummings, P. T.; Rosenqvist, J.; Wang, W.; Cole, D. R.; Anovitz, L. M.; Gasparovic, G. Physical Review E 2009, 79, 051504.

         (5)    Wei, M.-J.; Zhou, J.; Lu, X.; Zhu, Y.; Liu, W.; Lu, L.; Zhang, L. Fluid Phase Equilibria 2011, 302, 316.