N. C. Bera

Ab initio study of spectroscopic properties of RgCl (Rg=He, Ne, Ar, Kr) and their anions

Spectroscopic properties of HeCl, NeCl, ArCl, KrCl and their anions HeCl−, NeCl−, ArCl− and KrCl− in their ground state have been studied in detail using ab initio MP2, CCSD and CCSD(T) methods. These neutral molecules and their anions are weakly bound and their spectroscopic constants have been estimated using a method developed recently for calculating the spectroscopic constants of weakly bound molecule in Lennard–Jones potential. The net attractive force and the distance at which the net attractive force is greatest, have been calculated to get the physical picture. Most of the spectroscopic constants are first predicted. The calculated equilibrium bond length, dissociation energy and harmonic frequency agree very well with the experimental and theoretical values wherever available.

Dissociation and thermochemistry of methylsilanitrile and silylsilanitrile: implications for the chemistry of silicon in interstellar medium

Dissociation and thermochemistry of CH3SiN and SiH3SiN have been studied in detail using high level quantum chemical methods. The enthalpy of formation of these molecules at 0 K and 298.15 K are predicted by G3 and G3//B3LYP methods using an atomization scheme. The bond dissociation energy and energy barrier for the dissociation pathways are estimated at 0 K and the most energetically favourable dissociation products are predicted for the thermal decomposition reactions of the species in the gas phase. Finally, the enthalpy of dissociation for the most energetically favourable channel is calculated at 298.15 K. Among the four dissociation channels of CH3SiN, the most energetically favourable is SiN(2∑+) + CH3( ) having dissociation energy 57.4 kcal/mol. For SiH3SiN, dissociation channel SiN(2∑+) + SiH3( ) is the most energetically favourable, and its dissociation energy is about 1.4 kcal/mol higher than that of CH3SiN. The most energetically favourable dissociation channels may be a potential source of SiN radical in the interstellar medium.