Two new carbon allotropes (H-carbon and S-carbon) are proposed, as possible candidates for the intermediate superhard phases between graphite and diamond obtained in the process of cold compressing graphite, based on the results of first-principles calculations. Both H-carbon and S-carbon are more stable than previously proposed M-carbon and W-carbon and their bulk modulus are comparable to that of diamond. H-carbon is an indirect-band-gap semiconductor with a gap of 4.459 eV and S-carbon is a direct-band-gap semiconductor with a gap of 4.343 eV. The transition pressure from cold compressing graphite is 10.08 GPa and 5.93 Gpa for H-carbon and S-carbon, respectively, which is in consistent with the recent experimental report.
Cite
@article{arxiv.1203.5509,
title = {New Superhard Carbon Phases Between Graphite and Diamond},
author = {Chaoyu He and L. Z. Sun and C. X. Zhang and K. W. Zhang and Xiangyang Peng and Jianxin Zhong},
journal= {arXiv preprint arXiv:1203.5509},
year = {2012}
}
Comments
5pages,4figures,submitted to Phys.Rev.Lett on 18Jan12, transfer to Phys.Rev.B on 25Mar12; Solid State Communications(2012), http://dx.doi.org/10.1016/j.ssc.2012.05.022