Ab initio vibrational and thermodynamic properties of adamantane, sila-adamantane (Si10H16), and C9Si1H16 isomers

• Vibrational and thermodynamical properties of adamantane-like are presented.
• C9Si1H16, and Si10H16 are more stable energetically than adamantane.
• Thermodynamical results indicate that similar molecules could be synthesized.
• Sila-adamantane is more favorable to synthesize than others similar molecules.
• Starting from 630 K the synthesis of sila-adamantane could be spontaneous.

Vibrational and thermodynamic properties of adamantane molecule have been investigated using the density functional theory formalism considering both the generalized gradient and local density approximations. One or ten carbon atoms have been substituted with Si to form C9Si1H16 or Si10H16 (sila-adamantane), respectively. The vibrational normal modes, the infrared (IR) and Raman spectrum were analyzed and assigned for all the molecules. The present results for adamantane are compared with experimental and theoretical data of other researchers. In addition, for sila-adamantane our results are compared just with other theoretical data. Thermodynamical properties whose dependence with the temperature are discussed and a nice agreement between theoretical and experimental available data. The present quantum chemistry calculations indicate that all the derived molecular systems studied here could be synthesized, but sila-adamantane besides being more favorable to synthesize, has the advantage that for a temperature above 630 K, its reaction should occur spontaneously.

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