Thermal conductivity of diamond nanowires from first principles

Using ab initio calculations we have investigated the thermal conductivity ($\ensuremath{\kappa}$) of diamond nanowires, unveiling unusual features unique to this system. In sharp contrast with Si, $\ensuremath{\kappa}(T)$ of diamond nanowires as thick as 400 nm still increase monotonically with temperature up to 300 K, and room-temperature size effects are stronger than for Si. A marked dependence of $\ensuremath{\kappa}$ on the crystallographic orientation is predicted, which is apparent even at room temperature. [001] growth direction always possesses the largest $\ensuremath{\kappa}$ in diamond nanowires. The predicted features point to a potential use of diamond nanowires for the precise control of thermal flow in nanoscale devices.