High Accuracy Interatomic Potential Model for Binary Collision Approximation and Its Application into Sputtering Yield Estimation

To investigate the plasma-surface interaction (PSI) from the viewpoint of atomic-scale dynamics, binary collision approximation (BCA) and molecular dynamics (MD) are often used. An important factor common to these simulations in plasma irradiation is the model of the interatomic potential which can represent atomic collisions in the energy range above 10 eV. The famous model developed for the BCA is the Ziegler-Biersack-Littmark (ZBL) potential. Since the ZBL potential was formed as fitting function with 8 parameters, it requires low computational cost. The ZBL potential model is often used as the repulsive two-body term connecting to multi-body potential model for MD simulation. However, due to its small number of parameters, the reliability of the ZBL potential model is insufficient by comparison with the modern simulations such as machine-learning potential for MD. In the present work, higher accuracy interatomic potential model was proposed, which is named ReGenerated ZBL (ReGZ) potential. The ReGZ potential function was analytically derived from the spherical electron density of an independent atom which is expanded by the small number of terms. As a result, the number of atomic pairs is the square of the number of atomic elements, while the number of parameters required for the potential function is on the order of the number of atomic elements. Therefore, not only the error of potential energy is small but also computational cost is kept low. Furthermore, in the BCA simulation the difference from the ZBL potential appears on the sputtering yield and the reflection coefficient.