An Atomistic Description of the γ‑Alumina/Water Interface Revealed by Ab Initio Molecular Dynamics.
B. F. Ngouana-Wakou, P. Cornette, M. Corral Valero, D. Costa, and P. Raybaud.
Journal of Physical Chemistry 121 C, 2017, 10351−10363.
We report ab initio molecular dynamics (AIMD) simulations of the (100) and (110) γ-Al2O3/water interfaces at 300 K, using two sets of supercell models for each surface and two time lengths of simulation (10 and 40 ps). We first show that the effect of liquid water on the vibrational frequencies of hydroxyl groups at the interface varies according to the type of surface. This trend is explained by two key parameters affecting the interaction of both surfaces with water: the nature of the OH groups (i.e., μ1-OH, μ1-H2O, μ2-OH, and μ3-OH) and H-bond network among surface OH groups. The hydroxylated (110) surface favors the local structuration of water at the interface and the solvation of its μ1-OH and μ1-H2O groups by water similarly as in bulk liquid water. By contrast, on the (100) surface, a stronger H-bond network among μ1-OH and μ1-H2O groups reduces the water/surface interaction. We illustrate also how the interfacial interacting sites are spatially organized on the surfaces by two-dimensional maps of O–H distances. On both surfaces, the interfacial water layer orientation is predominantly Hup–Hdown. For long AIMD simulation time, Grotthuss-like mechanisms are identified on the (110) surface.
Strategies for the Growth of Large-Scale Self-Organized Structures. Wiame, F. Thin Solid Films 2017, 642, 258–275. https://doi.org/10.1016/j.tsf.2017.09.026.
Nanostructured surfaces are of fundamental importance in an ever-increasing number of applications. Strategies based on self-organization are a promising route for the controlled fabrication of nanostructured objects. Indeed, self-organization appears to be a much more frequent behavior than presumed and could be seen as a rule more than an exception. Nevertheless, in order to be practical and usable, the ability to tailor the size and dimensionality of the grown nanostructures is a prerequisite. This involves a full understanding of the fundamental aspects controlling self-organization mechanism.
The parameters governing the growth of self-organized surfaces are not yet fully understood. This may explain why their use is still limited. This review discusses a prototypical self-organized surface, namely, the O/Cu(110)-(2 × 1) surface and identifies the parameters which control the self-organization process and how they can be tuned. It is shown how these parameters can be varied by controlled co-adsorption of species at the surface in order to tailor the self-organization process and extend the range of achievable nanostructures.