On the structure of a new superhard hexagonal carbon phase

Zhang, Bin, Liang, Yongcheng, Guo, Zaoyang, Bordas, Stephane Pierre Alain ORCID: https://orcid.org/0000-0001-8634-7002, Lu, Jane W. Z., Leung, Andrew Y. T., Lu, Vai Pan and Mok, Kai Meng 2010. On the structure of a new superhard hexagonal carbon phase. Presented at: 2nd International Symposium on Computational Mechanics & 12th International Conference on Enhancement and Promotion of Computational Methods in Engineering and Science, Hong Kong, China, 30 November-3 December 2009. Proceedings of the 2nd International Symposium on Computational Mechanics and the 12th International Conference on the Enhancement and Promotion of Computational Methods in Engineering and Science, Hong Kong, 30 November - 3 December 2009. AIP Conference Proceedings (1233) Melville, NY: American Institute of Physics, pp. 489-493. 10.1063/1.3452220

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Abstract

Molecular dynamics simulations show that graphite will transform into a superhard phase under cold compression. Recent experiments show that there is a sp3‐rich hexagonal carbon polymorph (a0  =  2.496 , c0  =  4.123 ) with a bulk modulus of 447 GPa and average density about 3.6 g/cm3, restricted to the space group of P‐62c (No. 190), but the detailed atomic structure was not obtained [Wang et al., P. Natl. Acad. Sci. 101(38), 13699]. Here we set carbon atoms occupying P‐62c 4f Wyckoff positions of P‐62c, and calculate the total energy of the different structures changing the internal parameter z by first‐principles calculations using geometry optimisation algorithm in CASTEP code, which shows that the stable structures in energy (at local minimum points) are hexagonal carbon (z  =  1/4) and hexagonal diamond (z  =  1/16). The calculated mechanical properties and lattice parameters of the structure P‐62c 4f (z  =  1/4) are in good agreement with those of the new hexagonal carbon proposed by Wang et al., which indicates that the atomic structure is a possible candidate.

Item Type:	Conference or Workshop Item (Paper)
Date Type:	Publication
Status:	Published
Schools:	Engineering
Subjects:	T Technology > TA Engineering (General). Civil engineering (General)
Uncontrolled Keywords:	molecular dynamics method; elastic moduli; fullerene compounds; density functional theory
Publisher:	American Institute of Physics
ISBN:	9780735407787
ISSN:	0094-243X
Last Modified:	18 Oct 2022 14:27
URI:	https://orca.cardiff.ac.uk/id/eprint/17580

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