Accurate vibrational frequencies were calculated using the vibrational self-consistent field method (VSCF). The effect of anharmonicity of calculated frequencies on thermodynamic properties, such as entropy, was explored. The developments of the VSCF method were introduced in the manner in which potential energy surface (PES) is being generated. The comparison of harmonic, scaled harmonic and anharmonic frequencies, was made. Furthermore, the computing of a PES within the VSCF method was coarse-grain parallelized in order to enable calculations on bigger molecules. Finally, the work conducted on the reaction mechanism of the industrially important process of production of H2O2 catalyzed by gold nanoparticles is presented.