In order to analyse material surface processing, first-principles molecular-dynamics simulations are carried out. Density-functional theory, norm-conserving pseudopotential and plane-wave basis are used. Atomic, bond populations and local energy are proposed as estimation parameters of the stability of material surface atoms. As an example of application, H-termination process of Si (001) surface atom is numerically analysed. The results are the followings: The backbond strength of F-terminated Si surface atom decreases, and the Si atom shifts upward from the surface. When HF molecule attacks to the weakened Si backbond, the backbond vanishes and the H atom of HF moves to the Si atom of the second layer. From these results, it is confirmed that proposed method is useful to analyse surface chemical processes.
