Estudo teórico das hidratações dos íons Perclorato, Borohidreto e seus sais de sódio por meio da dinâmica molecular de Car-Parrinello

Abstract

The Car-Parrinello Molecular Dynamics with ultrasoft pseudopotentials of Vanderbilt was used to study the solvation effects on the conformational stability in aqueous solution of the perchlorate and tetrahydroborate ions and their salts with sodium, respectively. The calculations were carried on the canonic ensemble, with temperature kept at 298 K using the Nosé-Hoover thermostat. The molecular dynamics were carried out in vacuum for NaClO4 and NaBH4 in order to establish the coordination of Na+ cation with the anions to form the respective salts. Six cubic boxes were built to simulate the NaClO4 and NaBH4 salts in vacuum, perchlorate and tetrahydroborate ions surrounded by 61 water molecules each one, and for NaClO4 and NaBH4 surround by 85 water molecules each one. The steepest descendent and damped algorithms were used to minimize the Kohn-Sham energy, and the Verlet algorithm was used to integrate the equations of motion. The energy cutoff was fixed at 25 Ry and the fictitious mass was kept at 400 u. a. The energies of the electronic and ionic systems were monitored throughout the simulations. The effect of solvent on the properties of the solutes was investigated using the radial pair distribution function, coordination number, temporal variation of the dihedral angles and the bond lengths, diffusion coefficient, and mean residence time. The calculation results show that the solvent modifies the electronic and geometrical parameters of the solutes. These parameters are important in the investigation of chemical reactions between the ions studied and organics and/or inorganics reactants. The methodology discussed in the present dissertation can be applied in industrial and biotechnology processes.