The structures, stability, mechanical and electronic properties of a-boron and its twined brother a*-boron have been studied by first-principles calculations. Both a-boron and a*-boron consist of equivalent icosahedra B12 clusters in different connecting configurations of "3S-6D-3S" and "2S-6D-4S", respectively. The total energy calculations show that a*-boron is less stable than a-boron but more favorable than beta-boron and Gamma-boron at zero pressure. Both a-boron and a*-boron are confirmed dynamically and mechanically stable. The mechanical and electronic properties of a-boron and a*-boron indicate that they are potential superhard semiconducting phases of element boron.
@article{arxiv.1302.6417,
title = {Structures, stability, mechanical and electronic properties of a-boron and its twined brother a*-boron},
author = {Chaoyu He and Jianxin Zhong},
journal= {arXiv preprint arXiv:1302.6417},
year = {2013}
}