THEORETICAL CALCULATIONS FOR CATALYTIC ACTIVATION OF N-2 ON A MODELED IRON ADSORPTION SITE

MINDO/SR-UHF calculations were done on [FeN2]q(q = 1, 0 or -1) systems in end-on and side-on geometries in order to study the electronic and geometric factors that affect the adsorption of N2 on iron adsorption sites. All systems studied in the end-on geometry were found to be stable. The adsorption energy of N2 increases in the order: [FeN2]- > [FeN2]0 > [FeN2]+. The N-N bond is activated by the electronic transfer from Fe(q) to N2 in all cases, this effect is particularly large for the [FeN2]- system. Side-on interaction leads to thermodynamically unstable systems with a highly activated N2 molecule. Distortion energy curves show high energy barriers in going from end-on to side-on geometries and very low barriers for the inverse process.