- For gas phase studies of uni-molecular reactions we determine the activation energies (experimentally) , additionally we do computational methods like DFT using Gaussian.
- Here my doubt is how to tie the activation energy (Ea) with HOMO -LUMO energies of reactants and transition states
In the simplest term, activation energy is just the difference in electronic energy between the transition state and the reactant(s). So computationally, you have to optimize the transition state and reactant(s) and calculate the difference in energy - this should be a good estimate of the experimental activation energy.
Obviously the low activation energy should correspond to a small HOMO-LUMO energy gap (in reactant), but the correlation is much more complicated due to symmetry and other factors that may affect it.
Thank you very much dear Bartosz Trzaskowski .
- We have calculated the optimized (lowest energy) HOMO - LUMO of the transition state and the ground state of our compound (methyl butanoate) .
- My concern is from these data how we will reach on Ea.It is the difference between LUMO of the transition state and HOMO of reactant or something else?
- We have all the values , but while we computing the barrier gap(energy difference between LUMO of TS and HOMO of ground state) the value is much higher (0.365au~229kcal/mol) than real (67kcal/mol)
For more clarification, I have attached an image here . Kindly have a glance .
Expecting your reply
salaf
i am using CASTEP and i want to calculate activation energy for a dopant material. i dont know how to calculate it can you please help me to calculate it? Bartosz Trzaskowski
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