Fig. 5
A schematic scenario of the f-to-h phase transition. a The initial f-phase projected along [111] direction, in which cationic sites are randomly occupied by Ge, Sb, and vacancy. Red and green arrows denote the possible migration paths of the cationic atoms from layer I to layer II induced by thermal annealing. b The atomic configuration of i-phase after the migration process described in (a). Red and green arrows denote the possible migration paths of the cationic atoms from layer I to layer III via the transition layer II afterwards. c The atomic configuration of a deeper migration extent i-phase after the majority of Ge and Sb atoms in layer I have migrated, h-lattice-like atom arrangement makes the stacking block easily to slip to transition into h-phase. Orange arrow denotes the slip direction of the block. d The atomic configuration for the stable h-phase projected along [0001] direction, where Ge element prefers the inner cationic layers and Sb element likes the outer cationic layers in the blocks
