Fig. 1. (a and c) Top and side views of 2D group IV–V monolayers in the Td3 phase, (b and d) corresponding ones for the Td4 phase. The group IV- and V-atom centered polyhedrons are shown in the left panel of (a) for the Td3 phase, and shown in the right panel of (b) for the Td4 phase. The green arrows in (a and c) illustrate the transformation from the Td3 phase to the Td4 phase. The green dashed lines in (b) and (d) indicate the glide line and the mirror plane respectively.
