FlashSim: A novel particle-in-cell numerical model for vacuum surface flashover simulation based on finite element method. - Hao-Yan Liu; Guang-Yu Sun; Yue-Lin Liu; Shu Zhang; Chang-Chun Qi; Sheng Zhou; Wen-Rui Li; Guan-Jun Zhang (Comput. Phys. Commun., 2025)