Issue
EPL
Volume 87, Number 5, September 2009
Article Number 56003
Number of page(s) 6
Section Condensed Matter: Structural, Mechanical and Thermal Properties
DOI http://dx.doi.org/10.1209/0295-5075/87/56003
Published online 23 September 2009
EPL, 87 (2009) 56003
DOI: 10.1209/0295-5075/87/56003

Phase stabilities and mechanical properties of two new carbon crystals

Y. Liang1, 2, W. Zhang2 and L. Chen2

1   College of Engineering Science and Technology, Shanghai Ocean University - Shanghai 201306, China
2   State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences - Shanghai 200050, China

ycliang@shou.edu.cn

received 7 July 2009; accepted in final form 24 August 2009; published September 2009
published online 23 September 2009

Abstract
Density functional calculations are used to systematically evaluate phase stabilities and mechanical properties of two recently proposed carbon crystals (K4 and M-carbon), along with graphite, cubic diamond and hexagonal diamond. It is found that the K4 carbon, which can be referred to as a twin of the cubic diamond crystal, is mechanically unstable, implying that it cannot be formed. Remarkably, our calculations not only substantiate the M-carbon phase is a highly incompressible and potentially superhard material but also show that it exhibits mechanical stability. Moreover, a surprisingly small activation barrier (about 0.018 eV/atom) for the transformation of M-carbon to graphite explains some paradoxical experimental observations.

PACS
64.60.My - Metastable phases.
64.10.+h - General theory of equations of state and phase equilibria.
62.20.-x - Mechanical properties of solids.

© EPLA 2009