M585, a low energy superhard monoclinic carbon phase

A monoclinic carbon crystal, M585, consisting of ABCA-stacked cubic-diamond-segments interlinkecl by interfacial zigzag carbon chains is proposed based on first principles calculations. The formed linear 5-8-5 carbon grain boundary shows a totally new topological manner of carbon phase, which is distinct from those in the previously proposed 4+8 and 5-7-5 types. M585 is energetically more favorable than the previously proposed M-carbon, W-carbon, H-carbon and S-carbon and is dynamically stable. The calculations On electronic and mechanical properties of M585 indicate that it is optically transparent and mechanically superhard, which has potential applications in mechanical industry. (C) 2013 Elsevier Ltd. All rights reserved.