Theoretical Study of the Decomposition of BCl₃ Induced by a H Radical

Abstract

We report on a theoretical study of the gas-phase decomposition of boron trichloride in the presence of hydrogen radicals using ab initio energetic calculations coupled to TST, RRKM, and VTST-VRC kinetic calculations. In particular, we present an addition-elimination mechanism (BCl(3) + H → BHCl(2) + Cl) allowing for a much more rapid consumption of BCl(3) than the direct abstraction reaction (BCl(3) + H → BCl(2) + HCl) considered up to now. At low temperatures, T ≤ 800 K, our results show that a weakly stabilized complex BHCl(3) is formed with a kinetic law compatible with the consumption rate measured in the former experiments. At higher temperatures, this complex is not stable and then easily eliminates a chlorine atom. Our work also shows that a very similar mechanism, involving the same intermediate and sharing the same transition state, allows for the elimination of HCl. A dividing coefficient between these two elimination pathways is obtained from both a potential energy surface based statistical analysis and an ab initio molecular dynamics transition path sampling simulation. It finally allows partitioning of the global consumption rate of BCl(3) in terms of the formation of (i) BHCl(3), (ii) BHCl(2) + Cl through a H addition/Cl elimination mechanism, (iii) BCl(2) + HCl through a H addition/HCl elimination mechanism, and (iv) BCl(2) + HCl through direct abstraction.

Rare event simulations reveal subtle key steps in aqueous silicate condensation

“…Path sampling with Ab Initio molecular dynamics has been used before for the study of water autoionization, 42 fenton reactions, 43 gas-phase decomposition reactions, 44 and enzyme catalysis. 45 However, these papers are based on the original TPS 39 algorithm employing a single path ensemble of reactive trajectories.…”

Decomposition reaction rate of BCl3–CH4–H2 in the gas phase

“…Figure 7b shows that the logarithm of the decreasing rate for BCl 3 It should be noted that Ref. [40] reported a H radical attacking step of addition-elimination mechanism H+BCl 3 → BHCl 2 +Cl for the consumption of BCl 3 and the production of Cl radical and BHCl 2 (our IM33). This mechanism might also be important in our reaction system.…”

“…In Ref. [40], mechanisms of addition-elimination (AE) and direct abstraction (DA) of Cl atom in BCl 3 +H were investigated theoretically in detail to address the reaction of BCl 3 and the H radical that can be compared with an experimental observation at a condition of H at 2 Torr pressure. The present work has not involved this step mainly because we regard reaction (12) as the initialization for B production and the fact that H 2 has a much higher concentration than Fig.…”

“…By employing the additional Arrhenius rate constant of Ref. [40], 2.31 × 10 9 T 1.36 exp(−10.7 kcal/RT) cm 3 mol −1 s −1 , in the COMSOL entrance, we performed the calculations of the concentration distribution and obtained the results that are slightly different in some of the concentrations but unchanged in the apparent activation energy.…”

Machine learning and a computational fluid dynamic approach to estimate phase composition of chemical vapor deposition boron carbide

“…Their rate constants were calculated for temperatures within 200-2000 K and adopted G45-G58 [29]. Reinisch et al [30] reported a set of theoretical experiments of the gas-phase decomposition of boron trichloride in the presence of hydrogen radicals, and their reactions are also included (G59-G62 in Table 3). Note: The rate constants are written according to Arrhenius equation: K = AT n e −E/RT .…”