Abstract Thermodynamically stable cubic and orthorhombic NaCl3 as well as NaCl7 have been synthesized . A thermochemical explanation was recently propose  for the stability of such unusual compounds . In the present work, molecular modeling (SE-PM3/MMFF) of a dimmeric structure for NaCl3is performed. The calculated cation and anion charges, as well as bond distances for the NaCl3 gaseous dimmer are in good agreement with values for the solid Pm3nNaCl3 . To the modelled dimmer ΔfgHθ= -196.4 kJmol-1.For such dimmeric compound: point group C1; dNa-Na = 273.3 pm; dNa-Cl = 246.8-248.1pm; ZPE 10.01 kJmol-1; Hθ= -154.5 kJmol-1; Gθ = -289.3kJmol-1, Sθ = 425.1JK-1mol-1; Cv = 169.6JK-1mol-1).