Topological phase transition from T-carbon to bct-C16

The realization of nontrivial fermions in three-dimensional carbon allotropes greatly facilitates topological applications in carbon based-materials. In this work, we find a topological phase transition from T-carbon to bct-C 16 based on first principles calculations. After carrying out a heating or a doping process on T-carbon, a new carbon phase termed bct-C 16 is obtained. The potential energy and the crystal orbital Hamilton population confirm the phase transition process, respectively. Importantly, we also investigate the quantized Berry phase and drumhead surfaces states, confirming the topological nodal line semimetallic features of bct-C 16 . Due to the extremely weak spin–orbital coupling effect in carbon, the nodal ring in bct-C 16 can be guaranteed to be nearly intact. This work not only provides two methods to obtain the carbon phase bct-C 16 , but also an avenue for bct-C 16 to observe nontrivial fermions.