Ab initio modeling of dynamic stability of silicon prismanes

Abstract

We present the results of a study on the dynamic stability of silabiprismanes by means of the density functional theory. Silabiprismanes present an elementary case of a particular type of silicon nanotubes with an extremely small cross-section, constructed from dehydrogenated molecules of cyclosilanes (silicon rings). Unlike higher polysilaprismanes, they are formed by only three silicon rings and described by the chemical formula (Si n) 3 H 2n. In the presented study, we limited ourselves to the cases n = 5 ÷ 7. We focused on a detailed review of the mechanisms of isomerization and decomposition. Configurations of the corresponding transition states were determined, and the kinetic parameters in the Arrhenius law (activation energy and frequency factor) were evaluated. Silabiprismanes are found to be much more stable compounds than their carbon analogous. Their lifetimes at room temperature achieve hundreds of seconds, but at 200 K, their stability increases significantly. Thus, their lifetimes are sufficiently high for the identifying and studying of silicon biprismanes, but not for their industrial applications. Therefore, unsubstituted silabiprismanes require lower temperatures of operation, and their applicability is restricted. Although the general pyrolysis path is the same for all considered cages, its features strongly and non-monotonically depend on n. It is confirmed that the hexagonal and heptagonal silabiprismanes are much more stable than the pentagonal one. We obtained the absence of a direct correlation between the thermodynamic and kinetic stabilities of the silicon cages under consideration.

Metal ion-decorated hexasilaprismane and its derivative as a molecular container for the separation of CO2 from flue gas molecules: a computational study

“…Silicon analogs of the prismanes are also extensively studied in the literature. [19][20][21][22][23][24][25][26] To date, only the simplest silaprismanes, such as Si 6 H 6 , have been synthesized, 19 and the properties of the other analogs are predicted with theoretical studies. [20][21][22][23][24][25][26][27] It has been reported that substituting carbon atoms with silicon atoms stabilizes the prismane framework.…”

“…[19][20][21][22][23][24][25][26] To date, only the simplest silaprismanes, such as Si 6 H 6 , have been synthesized, 19 and the properties of the other analogs are predicted with theoretical studies. [20][21][22][23][24][25][26][27] It has been reported that substituting carbon atoms with silicon atoms stabilizes the prismane framework. 22 In a recent computational study, it was observed that the kinetic stability of Si 18 H 12 is higher than that of its carbon analog (C 18 H 12 ).…”

“…23 Since prismanes are metastable structures, their cages break at higher temperatures. 28 The stability of HSPs plays a crucial role in their practical applications, especially at high temperatures. In this study, we have considered the simplest form of silaprismane, Si 6 H 6 , that has been found to be stable up to a temperature of approximately 350 °C (ref.…”