We present a quantum-chemical study to elucidate the structure, energetics and stability of
isolated polymethylcubane molecules C 8 H 8–q (CH 3) q. The results obtained by means of
originally developed nonorthogonal tight-binding approach are in good agreement with the
existed experimental data for solid octamethylcubane C 8 (CH 3) 8. The isomerization
mechanisms for polymethylcubane family are studied in detail and the minimum energy
barriers' heights preventing the decomposition are calculated. The temperature dependence …