Water at a hydrophilic solid surface probed by ab-initio molecular dynamics: inhomogeneous thin layers of dense fluid.

We present a microscopic model of the interface between liquid water and a hydrophilic, solid surface, as obtained from \textit{ab-initio} molecular dynamics simulations. In particular, we focused on the (100) surface of cubic SiC, a leading candidate semiconductor for bio-compatible devices. Our results show that, in the liquid in contact with the clean substrate, molecular dissociation occurs in a manner unexpectedly similar to that observed in the gas phase. After full hydroxylation takes place, the formation of a thin ($\sim $ 3 {\AA}) interfacial layer is observed, which has higher density than bulk water and forms stable hydrogen bonds with the substrate. The liquid does not uniformly `wet' the surface, rather molecules preferably bind along directions parallel to the Si dimer rows. Our calculations also predict that at $\sim $ 1 nm, the structural and electronic properties of liquid water are weakly affected by one-dimensional confinement between hydrophilic, solid substrates. This work was performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.