Hartree-Fock (HF) method and density functional theory calculations of methanol to gasoline (MTG) reaction

We found interesting results regarding some thermodynamical parameters (Δ_rH^Θ, Δ_rG^Θ, Δ_rS^Θ of the MTG Reaction, and FTIR Spectra of methanol and dimethylether, using the Hartree-Fock method and Density Functional Theory (DFT) calculations at different computational levels. It is the aim of this paper to highlight these results. The GAUSSIAN 98 program was used to carry out the LCAO-MO-SCF calculations at the following levels: RHF/3-21g, RHF/6-31g, and DFT/B3LYP/d95**. Calculations at restricted Hartree-Fock levels (RHF/3-21g and RHF/6-31g) were performed since they are not as expensive as other levels (DFT/B3LYP/d95**). In the case of the HF method, working with larger basis set (6-31g) has improved the values slightly, which is as expected. We have noticed that performing calculations at higher levels (DFT/B3LYP/d95**) than the Hartree-Fock method does not dramatically improve the situation. Indeed, RHF is a reasonable approximation for many single gas phase molecule calculations. HF calculations at relatively small basis sets are adequate. The theoretical vibrational spectra of both methanol and dimethylether were compared with experimental results.