Molecular dynamics simulations of water and ions interacting with rutile surfaces

M. Předota

Institute of Physics and Biophysics, University of South Bohemia, Branisovska 31, Ceske Budejovice

predota@prf.jcu.cz

In the last 8 years we have been studying by molecular dynamics (MD) the dynamic and structural properties of aqueous solutions in contact with solid metal-oxide surfaces, rutile and cassiterite. During this period we obtained numerous results on structure of water and adsorbed ions, which were successfully linked with experimental results using X-ray techniques [1-3]. We gathered data on the adsorption of Rb⁺, Na⁺, Sr²⁺, Ca²⁺, and Zn²⁺ on neutral, negatively, and positively charged hydroxylated or nonhydroxylated 110 rutile surfaces.

In this communication, we summarize our results and outline the range of properties, which were studied on this system, including inhomogeneous diffusivity and viscosity [4] in the inhomogeneous interfacial region. We also describe the ab initio derived method to simulate charged surfaces at surface charge densities linked to solution pH values via surface titration experiments. Discussions with computational biophysicists about transferability of this study to e.g. interfaces with lipid membranes etc. and modeling of interactions of biomolecules with mineral surface are very welcome.

Figure 1. Hydrogen bonding at the neutral hydroxylated surface (left) and neutral nonhydroxylated rutile (110) surface (right) as extracted from a large periodic surface MD structures. Intramolecular O-H bonds in water (white) and surface hydroxyls (yellow), surface oxygen-water H-bonds (violet), surface hydrogen-water H-bonds (green). For the nonhydroxylated surface, water-water H-bonds are in red. Bond lengths are in Å.

References

1. M. Predota, A. V. Bandura, P. T. Cummings, J. D. Kubicki, D. J. Wesolowski, A. A. Chialvo, and M. L. Machesky, J. Phys. Chem. B, 108, (2004),12049.

2. M. Predota, Z. Zhang, P. Fenter, D. J. Wesolowski, and P. T. Cummings, J. Phys. Chem. B, 108, (2004),12061.

3. Z. Zhang, P. Fenter, L. Cheng, N. C. Sturchio, M. J. Bedzyk, M. Predota, et al., Langmuir, 20, (2004), 4954.

4. M. Predota, P. T. Cummings, and D. J. Wesolowski, J. Phys. Chem. C, 111, (2007),3071.