ABSTRACT:The gas-phase reactions between Pt 2 ϩ and NH 3 have been investigated using the relativistic density functional approach (ZORA-PW91/TZ2P). The quartet and doublet potential energy surfaces of Pt 2 ϩ ϩ NH 3 have been explored. The minimum energy reaction path proceeds through the following steps:In the whole reaction pathway, the step of d-2 3 d-3 is the rate-determining step with a energy barrier of 36.1 kcal/mol, and exoergicity of the whole reaction is 12.0 kcal/mol. When Pt 2 NH ϩ reacts with NH 3 again, there are two rival reaction paths in the doublet state. One is degradation of NH 4 ϩ and another is loss of H 2 . In the case of degradation of NH 4 ϩ , the activation energy is only 3.4 kcal/ mol, and the overall reaction is exothermic by 8.9 kcal/mol. Thus, this reaction is favored both thermodynamically and kinetically. However, in the case of loss of H 2 , the rate-determining step's energy barrier is 64.3 kcal/mol and the overall reaction is endothermic by 8.5 kcal/mol, so it is difficult to take place. Predicted relative energies and barriers along the suggested reaction paths are in reasonable agreement with experimental observations.