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-infinity h configuration. The pentaatomic ions can exist in the form of the D-infinity h linear isomer, C-2v planar cyclic isomer, or D-3h bipyramidal isomer. At similar to 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 Delta H-f(0) (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-).