Diagram of the three HCl + CH3 Cl + CH4 potential energy surfaces as a function of reaction coordinate. The two excited states in the diabatic representation break degeneracy due to spin-orbit coupling in the adiabatic representation, leading to a four fold degenerate ground state and a two fold degenerate excited state split by 882 cm−1.
HCl + CH3 Cl + CH4 stationary point geometries and Jacobi coordinate definition. Bond lengths given in Å.
Contour diagram of ground A1 (gray) and excited E (color) diabatic states for reaction HCl + CH3 Cl + CH4, computed from the basis set extrapolated surface model. Large δ corresponds to the Cl + CH4 reactant channel; small δ the HCl + CH3 channel. The surfaces are asymptotically degenerate but diverge in the interaction region, where the highest E contour lies 0.35 eV above the corresponding A1 contour.
Minimum energy path for the diabatic and adiabatic basis set extrapolated surfaces in Cl + CH4 channel. Spin orbit splitting for the adiabatic surfaces (−1/3, +2/3) shown for the asymptotic region in the inset. Diabatic surfaces: (black, dashed); adiabatic surfaces: (black, solid), (green), (red).
J-shifted thermal rate constants on the adiabatic ground state surfaces . (a) Forward reaction, for the IB surface. (b) Reverse reaction, for IB and Q//T surfaces. TST computed from IB ab initio energies.
The eight lowest hyperspherical adiabats for the HCl + CH3 Cl + CH4 reaction. Quantum states s = (i, ν) are asymptotically grouped in terms of vibrational quantum number ν. Asymptotic electronic states are A1: Cl (2P3/2) + CH4 (solid black), E: Cl (2P3/2) + CH4 (green), HCl + CH3 (blue, R) and E: Cl* (2P1/2) + CH4 (red). Potential ridge and minimum energy path along Cl + CH4 channel are given as black dashed lines; TS location indicated by red triangle.
(a) J = 0 reaction probabilities for the CH3 + HCl → CH4 + Cl(2P) reaction. CRP (red), nonadiabatic pathways (black, dashed). (b) Time delay analysis for identification of resonances (black). J = 0 CRP (red).
Initial state selected integral cross sections as a function of collision energy for reaction HCl(ν) + CH3 → Cl + CH4.
Initial state selected nonadiabatic branching ratio for HCl(ν) + CH3 → Cl(2P1/2) + CH4.
Ground state nonadiabatic cross section ratio for Cl* + CH4 → HCl + CH3.
Nonreactive inelastic probability for the Cl + CH4 (ν = 0) → Cl* + CH4 transition.
Basis set tests for reaction HCl + CH3 Cl + CH4. CCSD(T) relative energies in kcal mol−1; vibrationally corrected barrier heights shown in parentheses.
TS geometric parameters at MP2/cc-pV(T+d)Z-dk level of theory. Stationary point moments of inertia in amu× bohr2.
Harmonic frequencies for stationary points at the MP2/cc-pV(T+d)Z-dk level, in cm−1. Transition state frequencies are given prior to (pre) and following (post) curvilinear projection of explicitly treated vibrational modes.
PES parameters for the IB and the Q//T surfaces. The number of ab initio grid points (#) and the sum of squared residuals (SSR/a.u.2) are given for each surface. The total number of grid points including evaluated data is shown in parenthesis.
SOC surface parameters. Powers of 10 in parentheses. The number of ab initio grid points (#) and the sum of squared residuals (SSR/a.u.2) are given for each surface.
Energetic properties of ground state diabatic and adiabatic IB surfaces for reaction HCl + CH3 Cl + CH4. Energies given in kcal mol−1.
Scattering numerical parameters.a
Theoretical thermal rate constants for CH3 + HCl CH4 + Cl (2P3/2) on (IB). Rates given in cm3 molecule−1 s−1; powers of ten shown in parentheses.
Approximate location of nonadiabatic transition for the HCl + CH3 → Cl* + CH4 reaction.
Branching ratio model for nonadiabatic production of Cl*. Energies in cm−1, branching ratio at 1.3 eV.
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