Microporosity as a new property control factor in graphene-like 2D allotropes
We have performed a systematic study on the effect of microporosity on the energy stability and electronic properties of graphene-like materials, including 2D C, B and B–C allotropes. We used a modified crystal structure-search method to yield planar structures by systematically varying microporosity. Our results show that the energy stability of allotropes is strongly correlated with the microporosity and that the trends for C and B allotropes are qualitatively different. The formation energies of the most stable C allotropes with the same microporosity increase quickly with the microporosity, which shows a parabolic relationship. In contrast, B allotropes show a much weaker and linear dependence on microporosity. Our calculations also reveal that basic electronic properties such as metallicity and band gaps also depend strongly on the porosity. The allotropes with low microporosity and low formation energies tend to be metallic, and the semiconducting allotropes appear more often with high microporosity. In contrast to the general trend, our study identified a C allotrope with low microporosity that is quite stable and has a large band gap of 0.58 eV.