Optimization of interatomic potential for Si/SiO2 system based on force matching

In order to analyze the behavior of Si and SiO2, which are basic materials for the large-scale-integrated circuit technology, the molecular dynamics simulation has been widely used. For the simulation, it is necessary to select accurate interatomic potential function, which reproduces the force acting on each atom. However, the validity of potential functions proposed has not been discussed in terms of the force. In this study, the force calculated by the original Tersoff potential is compared with that obtained by an ab initio calculation in some snapshots of Si/SiO2 systems at the temperature of 300 K. It clarifies that the potential does not properly reproduce the force. Then, optimizing the parameters in the Tersoff potential on the basis of the force acting on each atom obtained by the ab initio calculation (force matching method), two modified functions are proposed. One is “Potential A” obtained by optimizing the parameters for the Si crystal and the β-cristobalite SiO2 crystal. The “Potential A” correctly reproduces not only the forces but also the lattice constants. However, it is not effective for Si/SiO2 interface. The “Potential B” obtained by optimizing the parameters for a Si/SiO2 interface model as well as the Si and the β-cristobalite SiO2 crystals. The forces and lattice constants are successfully reproduced for the interface as well. Moreover, the “Potential B” gives a good result for the β-quartz SiO2, which is not used for the optimization. This implies the versatility of the proposed function.