brydustin said:I was wondering if I do an IRC calculation and the energy range of the IRC does not quite reach the energy of the reactant or product of the system, do I need to make the IRC calculation "wider" (i.e. go more forward and reverse) so that I can interpolate the reaction coordinate of the system given the known energies of the reactants and products?
brydustin said:Energy (Relative to Transition as computed from IRC in Hartrees) = -0.02306;
with Rx Coordinate = -4.29864
Compared to:
Reactant with -0.028400 energy (Relative to Transition as computed in IRC in Hartrees)
I didn't do a frequency calculation because this requires more time; but I had the idea that I should probably want to find what reaction coordinate the reactant would coorespond to (however most of the literature doesn't actually concern itself with this); and I believe that the reaction coordinate is a bit of an abstraction anyway... i.e. what would it mean to interpolate a reaction coordinate for the reactant anyway?
I just figure it would be nice to label the IRC graph so that one could identify the products on a certain part of the graph and the reactants on the other.
I can't be sure that there would be no imaginary frequencies because I suppose I could have set the number of calculations ( # of reaction coordinates) to be higher (but that's precisely my question, I don't know if I should or not). I set it to do 70 (35 forward, 35 back; and that seems like quite a bit when compared to the default).
I agree this should be in computational physics, I click on the wrong link (sorry about that).
My basis for comparison was the energy which was calculated separately for a reactant energy/geometry optimization.
IRC (intrinsic reaction coordinate) calculations are used to study the path of a chemical reaction and determine the energies and geometries of the reactants, intermediates, and products along this path. They can also provide insight into the mechanisms and kinetics of the reaction.
The main data obtained from IRC calculations include the energies, geometries, and vibrational frequencies of the species along the reaction path. This information can be used to construct potential energy surfaces and calculate reaction rates.
The accuracy of IRC calculations is influenced by several factors, including the choice of the quantum chemical method, basis set, and level of theory. The quality of the initial molecular geometry and the choice of reaction coordinate also play a significant role.
IRC calculations are typically performed using quantum chemical software packages, which utilize algorithms to optimize the molecular geometries and calculate the energies and frequencies along the reaction path. The calculations can be performed at different levels of theory, from simple methods like Hartree-Fock to more advanced methods like density functional theory.
IRC calculations are used in a variety of applications in quantum chemistry, including the study of organic reactions, enzyme catalysis, and photochemical processes. They are also used to predict and design new chemical reactions and to understand and optimize reaction mechanisms.