ELECTRONIC-STRUCTURE, ULTRAVIOLET TRANSITION ENERGIES AND QUADRUPOLE COUPLINGS OF THE PLANAR HETEROCYCLES 2,1,3-BENZOXADIAZOLE, 2,1,3-BENZOTHIADIAZOLE AND 2,1,3-BENZOSELENADIAZOLE BY THE MS-LDA METHOD

Multiple-scattering local-density-approximation (MS-LDA) calculations, using both the X-alpha and VWN exchange-correlation functionals, were performed on the planar heterocycle 2,1,3-benzoxadiazole and its sulfur and selenium analogues. Ionization energies, first excited (ultraviolet) transition energies, dipole moments and nuclear quadrupole coupling constants were computed. The experimental photoelectron spectrum of the selenium compound was assigned. The influence of correlation and basis-set size on these properties was examined. Partial-wave population was performed to resolve ambiguities in the resonance structures.