Theoretical study of the structure and stability of the Na2Cl+, NaCl2−, Na3Cl2+, and Na2Cl3− ions

The geometrical parameters, normal vibration frequencies, and thermochemical characteristics of the Na2Cl+, NaCl2−, Na3Cl2+, and Na2Cl3− ions in saturated vapors over sodium chloride were calculated by the ab initio methods including electron correlation. According to calculations, the Na2Cl+ and NaCl2− triatomic ions have a linear equilibrium D∞h configuration. The pentaatomic ions can exist in the form of the D∞h linear isomer, C2v planar cyclic isomer, or D3h bipyramidal isomer. At ∼1000 K the Na3Cl2+ and Na2Cl3− ions exist predominantly in the form of the linear isomers. The energies and enthalpies of the ion-molecule reactions involving the above ions were calculated. The formation enthalpy of the ions ΔfH0(0 K) was determined: 230 ± 2 kJ/mol (Na2Cl+), −96 ± 4 kJ/mol (Na2Cl3−), −616 ± 2 kJ/mol (NaCl2−), and −935 ± 4 kJ/mol (Na2Cl3−).