Stability and crystal field splitting of N inf2 sup− in Barium Azide

The crystal field splitting of the ground²_g state and the equilibrium orientation of the N_inf2^sup– radical in the monoclinic barium azide are calculated employing a point ion representation of the lattice potential and assuming three different plausible trapping sites for the radical. When the N_inf2^– is assumed to replace an azide ion which is parallel to thec axis of the unit cell, the previously suggested trapping site, the calculated crystal field splitting is in order of magnitude agreement with the value deduced from theg shift in the ESR spectrum. The calculated orientational angle of the molecular axis with thec axis of the unit cell is 9.0 degrees which compares favorably with the experimentally determined angle of 5.0 ± 1.5 degrees. Possible reasons why the N_inf2^– can not be trapped at the site of an azide ion which is perpendicular to the c axis are suggested from the calculation.