Abstract
This work studies the ternary Si-C-N phases and exploiting an analogy between the NCN and O groups. Starting from the molecular model of and proceeding to extended models, we calculate that the energy hypersurface associated with the Si-N=C bond angle is very shallow, for both molecular and extended structures. We propose a crystal structure for the low-temperature modification in space group (95), which is lower in energy than an ideal cubic arrangement in space group A second structure, [space group (118)], is slightly higher in energy than but still more stable than the cubic structure, and may be the high-temperature structure of Both variants of show a small bulk modulus of about suggesting a high compressibility of these nonoxide covalently bonded materials. For we refined the crystal structure of the compound within the experimentally determined space group (41). We also found a second candidate nearly equal in energy, with space group differing only in the connection pattern of the layered sheets. Both ternary compounds appear to be thermodynamically unstable with respect to decomposition into C, and molecular
- Received 29 October 1998
DOI:https://doi.org/10.1103/PhysRevB.60.3126
©1999 American Physical Society