Using free-energy minimizations and three interatomic potentials, we calculated the structure of dodecasil-$3C$ without guest molecules at several temperatures. For this structure, the interatomic potentials predict substantially different free energies relative to $\alpha$-quartz. We find that dodecasil-$3C$ without guest molecules is triclinic for temperatures between 0 and 1200 K. The positions of the O atoms in the experimental structure of calcined dodecasil-$3C$ may not be well resolved. Furthermore, we present predictions for the elastic constants $C_{11}$, $C_{12}$, and $C_{44}$ that are in reasonable agreement with experiment on material with guest molecules. As we find that the symmetry of dodecasil-$3C$ is lower than cubic which was reported at the time of the elasticity measurements, it might be interesting to perform additional measurements on this compound to compare them with our predictions.

• Received 14 December 1995

DOI:https://doi.org/10.1103/PhysRevB.53.14073