NEW REACTION PATHWAYS OFPROPENE + BCl₃DECOMPOSITION IN CHEMICAL VAPOR DEPOSITION PROCESS

Abstract

More reaction pathways in the CVD process of preparing boron-carbides with BCl 3 -C 3 H 6 (propene)-H 2 precursors were examined in addition to the \lowest" path proposed by Jiang et al. in Theor Chem Acc 127:519À538, 2010. The new pathways investigated in this work involve 81 new transition states and 79 new intermediates. Geometries of the species were optimized with the density functional theory at B3PW91/6-311G(d,p) level. Intrinsic reaction coordinates were analyzed to confirm the correct reaction linkages. Energy barriers and reaction energies were calculated with the accurate model chemistry method G3(MP2) after a non-dynamical electronic correlation detection using CASSCF method. Heat capacities and entropies were obtained with the statistical thermodynamics and fitted as a function of temperature. Gibbs free energies at 298.15 K and 1200 K were used to examine the reaction paths. It was found that some steps in the new paths at both 298.15 K and 1200 K are different from the \lowest" path obtained previously and the pathways for the new products CB and C 2 B were obtained.

Decomposition Reaction Rate of BCl3–C3H6(propene)–H2in the Gas Phase

“…In refs and , the most favorable reaction pathway for the decomposition reactions of the BCl 3 –C 3 H 6 –H 2 system is presented for different products C 3 B, C 2 B, and CB, within which some differences will be noted in the text.…”

“…Within these reactions, a superscript Q denotes that the species is from the work by Qu et al in ref , a superscript H denotes that the species is from the work by Han et al in ref , a superscript J denotes that it is from the work by Jiang et al in ref , and a superscript Y denotes that the species is from the work by Yang et al in ref . All the species, the structure, symmetry, and the electronic state are shown in Figure .…”

“…All the geometry optimizations and frequency (as well as the Hessian matrix) calculations of the MEPs and the selected points along the MEPs are calculated with density functional theory (DFT) at B3PW91/6-311G(d,p) , level. The energies are further refined with the accurate model chemistry method G3(MP2). , Because the dominant configuration coefficients of the TSs and the intermediates are larger than 0.9, , the single reference state method is believed reasonable. The rate constants (high pressure limited) were calculated with the variational transition state theory (VTST), , which is designed to vary the dividing surface along the MEP to minimize the rate and to minimize the error of the “recrossing” trajectories.…”

“…Actually, the gas phase dissociation reactions should be one of the major problems that needs to be investigated in addition to the gas phase nucleation, gas phase diffusion, surface diffusion, and the heterogeneous surface reactions (atomic or molecular absorptions, formation of complexes, possible reactions of replacing atoms, or the dissociation of the H or Cl atoms) processes. To reveal the mechanisms of the complicated reaction system, theoretical investigations were carried out on the thermodynamics for the equilibrium distribution of the species with 325 gas phase molecules and reaction pathways involving 182 intermediates and 176 transition states. , Consequently, the most favorable pathway examined so far from refs and was also reported, which includes 18 steps to produce gas phase C 3 B, 13 steps to produce CB, and 10 steps to produce C 2 B, including reaction chain initializations for each product.…”

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

“…Also in the theoretical study of reaction thermodynamics, 325 possible gaseous species were identified in the homologous reaction system of BCl 3 -C 3 H 6 (propene)-H 2 precursors [17]. In the study of the reaction paths and kinetics of BCl 3 -propene-H 2 system, 182 intermediates and 176 transition states (TSs) were found [18][19][20] with the first principles.…”