Thermal rectification at water/functionalized silica interfaces

Using nonequilibrium molecular dynamics simulations, we study the thermal diode effect in a system composed of silica, self-assembled monolayers (SAMs) at the silica surface and water surrounding this system, by imposing a series of positive and negative heat currents. We have found that in the limit of large heat currents, the thermal conductance at the SAMs-water interface is about 1000 MW/m(2) K at room temperature for heat flowing from the SAMs to the water and 650 MW/m(2) K for heat flowing from the water to the SAMs, respectively, resulting in a thermal rectification of up to 54%. Analysis of the radial distribution function of oxygen-oxygen atoms in water indicates that the origin of the thermal rectification resides in the strong temperature dependence of the hydrogen bonds in water. (C) 2009 American Institute of Physics. [doi:10.1063/1.3247882]