Theoretical Investigations for Kinetics of the Chemical Reactions: H + SiCl_x (x = 1, 2, 3)

Abstract

Hydrogen atoms and SiCl x (x = 1, 2, 3) radicals coexist during the hydrogenation of silicon tetrachloride (STC, SiCl 4 ), an important process in the fabrication of industrial polysilicon. In this work, the mechanisms and kinetics of the reactions between H and SiCl x (x = 1, 2, 3) were studied by theory. The structures and vibrational frequencies of reactants, products, intermediates, and transition states (TSs) were determined at the B2PLYP/may-cc-pVTZ level. The single-point energies of minima and saddle points were refined using the coupled-cluster single− double with triple perturbative (CCSD(T)) with the complete basis set extrapolation method. Some special treatments were designed to obtain reliable wave functions for unimolecular reactions without tight TSs by the density functional theory. Subsequently, Lennard-Jones (L-J) parameters between each intermediate (SiHCl x ) and bath gas (He) were obtained at the MP2/jul-cc-pVTZ level to derive reliable temperature-and pressure-dependent rate coefficients for unimolecular reactions according to the variational Rice−Ramsperger−Kassel−Marcus theory. For bimolecular reactions, rate coefficients were determined by the variational transition-state theory. The rate coefficients of barrierless reactions were derived based on the loose TSs with the maximum free energy. Finally, the master equation analysis was used to investigate the variation of the rate coefficients with pressure and temperature in the activated paths.

Theoretical kinetics investigations of the reaction HO + SO ↔ H + SO2 on an accurate full‐dimensional potential energy surface

“…As shown in Figures S7–S9 in SI, the CCSD(T)‐F12a/AVTZ calculated interactions deviate remarkably from the L–J potential. Indeed, the interactions between target species and Ar depend significantly on the orientation, which was crudely approximated to be isotropic in the L–J potential 74,75 …”

“…Indeed, the interactions between target species and Ar depend significantly on the orientation, which was crudely approximated to be isotropic in the L-J potential. 74,75 The species population versus time of H, HSO 2 , HOSO, SO⋅⋅⋅HO, and HO are depicted in Figure 13A for 300 K and Figure 13B for 800 K, respectively, both at 1 atm. It can be seen from Figure 13A that the reaction reaches equilibrium at 10 −6 s. SO⋅⋅⋅HO or HOSO cannot be accumulated because the consumption is too fast.…”

Understanding the kinetics and atmospheric degradation mechanism of chlorotrifluoroethylene (CF2CFCl) initiated by OH radicals

“…Lastly, the average values were used as the target interactions' collision parameters. 56 Lennard-Jones collision rate theory was utilized to calculate collisional stabilization rate constants. 57 The L-J collision parameters of the energized adducts, 58 [CTFE-OH]˙ are estimated as σ = 5.1 Å and ε / k B = 418.4 K with air as a bath gas ( σ = 3.711 Å and ε / k B = 78.6 K, M = 28.81 g mol −1 ).…”

Pressure Dependence of Rate Coefficients of Unimolecular and Chemical Activation Reactions Connected to the Potential Energy Wells of Si2H2Cl4, Si2Cl6, and Si2Cl4 via Rice–Ramsperger–Kassel–Marcus Calculations

“…Although CCSD(T) is a single-reference based method, Walch and Dateo showed that accurate energetics of the reactions of SiCl 2 and SiHCl with H and Cl atoms can be obtained by using CCSD(T). 10 Zhang et al 11 also adapted the single-reference calculation method CCSD(T)/jul-CBS//B2PLYP/may-cc-pVTZ and found it to be an appropriate level for the unimolecular decomposition of SiHCl x ( x = 1, 2, and 3) including Si–H or Si–Cl bond breaking reactions. In our previous work, 6 we also studied the breaking bond reactions using GAMESS at the multi-reference CR-CC (2,3)/CBS//UB3LYP/6-31+G(d,p) level of theory 12 but found discontinuity in energy as the bond length increased for some of the reactions and virtually no difference from the results obtained at the UCCSD(T)/CBS//UB3LYP/6-31+G(d,p) for other reactions.…”