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Published May 5, 1995 | metadata_only
Journal Article

Is carbon nitride harder than diamond? No, but its girth increases when stretched (negative Poisson ratio)


It has been believed that C_3N_4 ceramic would be harder than diamond. Predictions are reported of the mechanical properties based on a force field derived from ab initio quantum mechanics. The predicted structure for α-C_3N_4 is in good agreement with transmission electron diffraction (TED) studies, supporting the identity of the films as α-C_3N_4. The bulk modulus of α-C_3N_4 is calculated to be 189 GPa, significantly less than diamond (436 GPa calculated, 442 GPa experimental). However, α-C_3N_4 is predicted to have a negative Poisson ratio. This may lead to interesting applications.

Additional Information

© 1995 Elsevier. Received 21 December 1994, Accepted 21 February 1995. The research was funded by the NSF (CHE 91-100289). Some of the computations were carried out at the NSF Pittsburgh Supercomputing Center or on the JPL-Cray. The facilities of the MSC used in this research were supported by grants from DOE-AICD, NSF-ASC, Allied-Signal Corp., Asahi Chemical, Asahi Glass, Chevron Petroleum Technology, BF Goodrich, Hughes Research, Teijin Ltd, Vestar, and Beckman Institute

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August 20, 2023
August 20, 2023