Kinetics of Substituted Silylene Addition and Elimination in Silicon Nanocluster Growth Captured by Group Additivity

Abstract

Accurate rate coefficients for 40 bimolecular substituted silylene addition reactions for silicon hydrides containing up to nine silicon atoms are calculated using the G3//B3LYP method. The overall reactions exhibit two steps: the reactants first meet to form an adduct, which then converts into a saturated silicon hydride. Values for the single-event Arrhenius pre-exponential factor, A, and the activation energy, E(a), are calculated from the G3//B3LYP rate coefficients corrected for internal rotations, and a group additivity scheme is developed to predict A and E(a). The values predicted by group additivity are more accurate than structure-reactivity relationships currently used in the literature, which rely on representative A values and the Evans-Polanyi correlation. The structural factors that have the most pronounced effect on A and E(a) are considered, and the presence of rings is shown to influence these values strongly.

Thermal Decomposition of Branched Silanes: A Computational Study on Mechanisms

“…Silylene insertion : Scheme shows two reaction pathways of silylene insertion into a SiH bond of a terminal silyl group (first reaction) or a SiSi bond (second reaction). Insertion into a SiH bond can proceed via an encounter complex ( X‐15 ) which only exists for trisilane ( T‐15 ) 35. Furthermore, according to the findings for the 1,2‐H shift, only transition states with staggered conformation ( X‐16 a_ts ) were taken into account, as they exhibit the lowest activation barriers (Figure 2).…”

“…Insertion into a SiÀH bond can proceed via an encounter complex (X-15) which only exists for trisilane (T-15). [35] Furthermore, according to the findings for the 1,2-H shift, only transition states with staggered conformation (X-16 a_ts) were taken into account, as they exhibit the lowest activation barriers (Figure 2). Neopentasilane is an exception, as we were unable to locate a transition state with staggered conformation.…”

Data‐Driven Investigation of Monosilane and Ammonia Co‐Pyrolysis to Silicon‐Nitride‐Based Ceramic Nanomaterials

“…The G3//B3LYP level of theory was also preferred for self-consistency because our previous studies used the same level of theory . [33][34][35][36][37] In this study, however, due to a large electronegativity difference between N/Si and N/H atoms, more flexible basis sets were potentially needed and explored. For this purpose, we added different levels of polarization functions and diffusion functions to the B3LYP functional.…”

“…In short, the singlet state was lowest energy electronic wavefunctions used in our investigation, and the G3/B3LYP composite method was most accurate for thermochemistry prediction against available experimental data for Si and N containing hydrides. The G3//B3LYP level of theory was also preferred for self‐consistency because our previous studies used the same level of theory [33–37] . In this study, however, due to a large electronegativity difference between N/Si and N/H atoms, more flexible basis sets were potentially needed and explored.…”

Synthesis of silicon nanoparticles with a narrow size distribution: A theoretical study

“…The result was a total of 2615 reactions with 221 silicon hydride species (Swihart & Girshick, 1999). More recently, automatic mechanism generation was used to generate a mechanism with 8076 reactions among 1398 species for clusters up to eight silicon atoms (Wong et al, 2004) and quantum chemical calculations were undertaken to investigate the molecular transition steps involved in the decomposition of silane (Adamczyk et al, 2009(Adamczyk et al, , 2010.…”