Оптимальность и точность компьютерных вычислений свободной энергии Гиббса гидратации молекул в континуальных моделях сольватации

Abstract

  In this paper, computer simulations of dissolving some small organic molecules: methanol (CH3OH), ethanol (CH5OH), acetamide (H3CC(O)NH2), methanethiol (CH3SH), methylamine (CH3NH2), chloromethane (CH3Cl) in water and calculations of the Gibbs free energy of hydration are performed. Calculations of the free energy of hydration are carried out within the framework of two well-known continuum solvation models: Solvation Model of Density (SMD) and Conductor-like Polarizable Continuum Model (CPCM). The quantum-mechanical part of the calculations is performed by the method of the hybrid density functional b3lyp and the restricted Hartree-Fock method. A comparative assessment of the accuracy and timing of calculations using different methods has been carried out. The versatility, high accuracy, and low consumption of calculation time using the SMD in a frame of the density functional method b3lyp are shown. In comparison with experimental data, errors of the values of the free Gibbs energy of dissolution of molecules in water are not exceeded 20 percent. The two modified CPCM models demonstrate worse results regarding accuracy and time consumption than the SMD approach. In this case, the restricted Hartree-Fock method turns out to be preferable compared to the density functional method b3lyp.