SOURCE:
The starting expression for k(121) in the GRI-Mech 3.0 optimization was from Eiteneer et al. (JPC 1998), which was obtained by a least-squares fit of recent experimental data with a fixed T^2.5 term . Optimization based only on Eiteneer et al's experiments (targets BCO.T1-T7) did not change k(121). However, joint optimization with targets from the work of Hidaka et al (IJCK 1993) (BCH2O.T1-T3) approximately doubled the starting expression.
The temperature range of the targets sensitive to k(121) is narrow, 1250-1600 K. Lower temperature data ( Baldwin and Walker at 773 K and Jemi-Alade et al. at 541-656 K) is fit by the starting expression but overpredicted by the optimized expression. Therefore, a new final rate coefficient expression was chosen to fit both the lower temperature results and the optimized rate constants in the 1250-1600K range, using a T^2 term.
This new expression, k(121)=5.6e6 T^2 exp(-12000/RT) is within +/- 3% of the optimized expression in the range 1250-1600 K.
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Temp delta-S delta-H kf kr Keq
(K) (cal/mol K) (kcal/mol) ----(mol,cm3,s)----- (cm3/mol)
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300 2.6 .5 9.13E+02 5.76E+02 1.59E+00
500 3.4 .8 7.96E+06 3.25E+06 2.45E+00
1000 4.0 1.2 1.34E+10 3.29E+09 4.05E+00
1500 3.9 1.2 2.25E+11 4.55E+10 4.95E+00
2000 3.8 .9 1.09E+12 2.02E+11 5.41E+00
2500 3.6 .5 3.13E+12 5.57E+11 5.61E+00
3000 3.5 .1 6.73E+12 1.19E+12 5.68E+00
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