Dimers of the CL-20 derivatives
According to the previous studies,\cite{Degtyarenko_2014,Katin_2017} CL-20 molecules can form covalent dimers via the methylene molecular bridges (see Fig. 3a). Similar dimers can be constructed from the CL-20 derivatives. Dimers of CSi5H6N12O12 and C4Si2H6N12F12 have three and eight possible isomers, respectively. These isomers differ from each other by the relative positions of silicon atoms. Structures of all isomers as well as their relative energies are presented in Fig. 3. One can see that the isomers in which carbon atoms are located far from the methylene bridges possess lower energies. This rule holds true for all dimers of both CSi5H6N12O12 and C4Si2H6N12F12 systems. So, the presence of silicon close to the methylene bridges promotes the dimers formation. Unfavorable location of carbon atoms close to the methylene bridges results in increasing of internal energies by at least ~0.14 eV and ~0.32 eV for the dimers of CSi5H6N12O12 and C4Si2H6N12F12, respectively. These values are much higher than the typical thermal energies kT (even at high temperature of 1000 K kT ~ 86 meV). So, the formation of unfavorable dimers is improbable.