Adsorption behavior of N2 on Pd surface

Based on the relativistic effective core potential (RECP/SDD) for Pd atom and AUG-cc-pVTZ basis function for N atom, the structure of PdN and PdN2 have been optimized using B3LYP method, and the thermodynamic functions for PdN and PdN2 have been calculated. The vibrational energy, electronic and vibrational entropy of the molecules in their solid states are assumed, Delta H-circle minus, Delta S-circle minus and Delta G(circle minus) and nitrogen equilibrium pressures of the nitrogenating reaction have been calculated based on this approximation. It is deduced that at 1.01325x10(5)Pa and 298.15 similar to 998.15 K, adsorption of N-2 on Pd surface proceeds as Pd(s) + N-2 = PdN2(S). The formation enthalpy for PdN (s) at 298.15 K is 254.37 kJ(.)mol(-1), and the formation enthalpy for PdN2(s) at 298.15 K is -80.59 kJ(.)mol(-1). The nitrogen equilibrium pressure is about 100 times of the hydrogen equilibrium pressure, so it is difficult for Pd to adsorb N-2.