Phonon interference and anharmonicity effects in nanoconstrictions

We perform classical nonequilibrium molecular dynamics simulations to calculate heat flow through two-dimensional rectangular, hourglass-shaped and circular microscopic constrictions connecting two large reservoirs. The reservoirs are also included in the simulations to account for the details of phonon transfer both in the bulk and at the bulk-constriction interface. We show that, in the nearly ballistic limit, there exist local minima and maxima as well as strong directional patterns in the temperature and heat current profiles. The directional patterns are shown to take place along crystallographic < 11 > directions for all simulated geometries, which suggests that the directionality is strongly linked to the crystal structure.