Ab initio parameterized valence force field for the structure and energetics of amorphous SiO_x (0≤x≤2) materials

We present a modified valence force field model for the structure and energetics of amorphous silicon suboxides (a-SiO_x, 0 ≤ x ≤ 2). The parameters are optimized to fit the results from cluster and periodic density-functional theory (DFT) calculations of various model structures. The potential model well reproduces the DFT energetics of various a-SiO_x systems for all O:Si composition ratios. We also examine how the choice of force fields affects the atomic-level description of phase separation in a-SiO _x and a-Si/a-SiO₂ interfaces using a continuous random network model-based Monte Carlo approach. The results highlight the critical role of the relative rigidity between Si and SiO₂ matrices in determination of the structural properties of the Si/SiO₂ composite system, such as interface bond topology, degree of phase separation, and abruptness of the interface.