1 QUANTUM-CHEMICAL CALCULATION OF SOME THERMODYNAMIC PROPERTIES OF GASEOUS AND HYDROTHERMAL SYSTEMS

The ab-initio calculations of equilibrium geometry, vibrational frequencies, thermodynamic properties of unusual molecule Si2O2 (a product of impact process, as O.I.Jacovlev, GEOHI, has reported) also as calculation of full energy of crystalline silica and thermodynamic properties of aqua species HF, HCl, Cl-, F- and dissociation constants of HF and HCl acids were performed. All calculations were done by the use of GAMESS programs [1, 2]. The restricted Hartry-Fock level and Møller-Plesset second order perturbation theory (except a full energy calculations of silica) were selected for our calculation. The basis DH+G* * was used. For the Si2O2 and SiO molecules the full energy of molecules including the Gibbs free energy EGT = Eform + GT was calculated at temperatures 298K and 2000K. These values allowed to obtain the Gibbs free energy ∆rGoT for reaction 2SiO =Si2O2 and Gibbs free energy ∆fGo298 of formation Si2O2 in standard condition. We obtained ( in kcal/mol): for SiO EG298 =-228473.5, EG298 =-228576.5 for Si2O2 EG298 =-456946.2, EG2000 =-457124.8 Hence, ∆rGo298 = +0.8kcal/mol; ∆rGo2000 = +28.2kcal/mol The usage of Gibbs free energy of formation of SiO: ∆fGo298 =-30.45±2 kcal/mol [3] allowed us t