Nowadays, theoretical computational chemistry is developing rapidly. Scientists often use quantum chemistry methods to calculate reaction path based on experimental exploration and propose new or verify the existing chemical reaction mechanism. Examination of reaction paths helps to determine the role of the catalyst, explain the selectivity of the reaction, and obtain the thermodynamic and kinetic data of the reaction. The calculation of the reaction path is an important part of the study of reactivity. The easiest way to calculate the reaction path is to start from the saddle point and proceed step by step along the negative gradient direction, and this method of steepest descent leading to the minimum energy path. It is necessary to study the highest saddle point, because the overall reaction rate depends on the height of the reaction barrier. Reaction paths can be used to reveal intermediate structures, and connect reaction barriers to the correct reactants and products.
Advantages of Reaction Paths Examination
- Improve the possibility and efficiency of successful reaction.
- Reduce reagent consumption.
- Establish the molecular configuration required for calculation
We modify the reactant to establish the product model. The purpose is to ensure that the atoms of the reactant and the product can be matched one by one when facilitate the establishment of the reaction path, thereby creating a reasonable trajectory from the reactant to the product.
- Calculate the reaction path and analyze the calculation results
- Use modules to optimize the obtained reaction path
Figure 1. DFT calculations of DMC reaction paths on SAs Rh-CeO2 NWs and Rh/CeO2 NWs. (Bai, S.; et al. 2020)
At Alfa Chemistry, we apply a diversity of quantum methods to perform rapid examination of reaction paths using first-principles calculations, density functional theory calculations and ab initio structure calculations. Our examination of reaction path include the following:
- First-principles thermodynamic calculations
We use first-principles thermodynamic calculations for the possible metastable paths of a chemical reaction. Our experts can find the minimum free energy path among all the possible paths which is the most stable reaction path. Moreover, we can assess the predicted mechanisms under the DFT uncertainty.
- Density functional theory calculations
For multistep catalytic reactions, a large number of possible reaction paths can be envisioned. At Alfa Chemistry, we have developed various possible kinetic models, each containing a significant number of parameters. Our teams apply DFT calculations, in combination with experimental surface science data, to elucidate the reaction path of some complex reaction mechanisms. Moreover, in order to improve the accuracy of the cluster DFT energies, accurate gas phase standard enthalpies of formation are determined for all reaction intermediates, either from experimental data or from high level CBS-QB3 calculations.
- Ab initio electronic structure calculations
We introduce ab initio electronic structure calculations and generalized transition-state theory to generate the minimum energy path of a chemical reaction. The convergence with respect to step size of the geometry and energy along this path is studied with several algorithms. We also provide the extensive calculation of chemical reaction rate coefficients by interfacing the POLYRATE code for variational transition-state theory and semiclassical tunneling calculations with a locally modified GAUSSIAN82 electronic structure package that now contains reaction path following capabilities at both the Hartree-Fock and perturbation theory levels.
Why Choose Us?
- Our examination of reaction paths services help to deepen the understanding of the reaction steps a molecular level, allowing to further optimize the catalyst selectivity towards the desired product.
- We are committed to finding dominant path along which activation energies are lower than along any other possible path branching from this dominant path, and determine if there is a rate determining step along the reaction path.
Examination of reaction paths provides an effective way to optimize the chemical process. Our examination of reaction paths services remarkably reduce the cost, promote further experiments, and enhance the understanding of chemical process for customers worldwide. Our personalized and all-around services will satisfy your innovative study demands. If you are interested in our services, please don't hesitate to contact us. We are glad to cooperate with you and witness your success!
- Bai, S.; et al. High-efficiency direct methane conversion to oxygenates on a cerium dioxide nanowires supported rhodium single-atom catalyst. Nature Communications. 2020.