Theoretical Study of the Direct Conversion of Methane …
31
Fig. 4 Potential-energy diagrams (including the zero-point energy) along the reaction pathway,
MO + + CH 4 → M + + CH 3 OH, in the high-spin and low-spin states. Relative energies are in
kcal/mol. Reproduced from Ref. [36]. Copyright 2000 American Chemical Society
3.6 kcal/mol from 12.3 kcal/mol of HI. The surface crossing between the quartet and
septet energy surfaces occurs in the vicinity of TS2. Because all reaction species in the
MnO
+ /CH 4 system lie lower in energy than the dissociation limit, the initial energy is
sufficient to overcome TS1 and TS2. Therefore, the crossing point of the MnO
+ /CH 4
system does not contribute to the reaction via TS2 compared with the crossing point
of the CrO
+ /CH 4 system. The overall reaction energies in the MnO
+ /CH 4 system are
exothermic: 6.3 kcal/mol in the quintet state and 26.2 kcal/mol in the septet state.
31
Fig. 4 Potential-energy diagrams (including the zero-point energy) along the reaction pathway,
MO + + CH 4 → M + + CH 3 OH, in the high-spin and low-spin states. Relative energies are in
kcal/mol. Reproduced from Ref. [36]. Copyright 2000 American Chemical Society
3.6 kcal/mol from 12.3 kcal/mol of HI. The surface crossing between the quartet and
septet energy surfaces occurs in the vicinity of TS2. Because all reaction species in the
MnO
+ /CH 4 system lie lower in energy than the dissociation limit, the initial energy is
sufficient to overcome TS1 and TS2. Therefore, the crossing point of the MnO
+ /CH 4
system does not contribute to the reaction via TS2 compared with the crossing point
of the CrO
+ /CH 4 system. The overall reaction energies in the MnO
+ /CH 4 system are
exothermic: 6.3 kcal/mol in the quintet state and 26.2 kcal/mol in the septet state.