  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.
