Structure, Energy, and Thermal Transport Properties of Si-SiO$_2$ Nanostructures using an Ab initio based Parameterization of a Charge-Optimized Many-Body Forcefield

In an effort to extend the reach of current ab initio calculations to simulations requiring millions of configurations for complex systems such as heterostructures, we have parameterized the third-generation Charge Optimized Many-Body (COMB3) potential using solely ab initio total energies, forces, and stress tensors as input. The quality and the predictive power of the new forcefield is assessed by computing properties including the cohesive energy and density of SiO$_2$ polymorphs, surface energies of alpha-quartz, and phonon densities of states of crystalline and amorphous phases of SiO$_2$. Comparison with data from experiments, ab initio calculations, and molecular dynamics simulations using published forcefields including BKS (van Beest, Kramer, and van Santen), ReaxFF, and COMB2 demonstrate an overall improvement of the new parameterization. The computed temperature dependence of the thermal conductivity of crystalline alpha-quartz and the Kapitza resistance of the interface between crystalline Si(001) and amorphous silica are in excellent agreement with experiment, setting the stage for simulations of complex nanoscale heterostructures.