ABINITIO DETERMINATION OF THE EQUILIBRIUM GEOMETRY AND VIBRATIONAL FREQUENCIES OF BORAZINE

The equilibrium structure of borazine, B3N3H6, has been optimized at the HF-SCF level using the 6-31G, 6-31G*, 6-31 + G*, 6-31 + + G**, 6-311G**, DZP and TZP basis sets and at the second-order Moeller-Plesset perturbation theory, with all orbitals active, with the 6-31G* basis set (MP2/6-31G*). The D3h symmetry conformation is established to be, at all the adopted levels of theory, the global minimum of the molecule. The planar structure has been studied employing several basis sets and the effects of basis set extension and of polarization d-functions on the molecular geometry are discussed. The bond distances and the ring angles of borazine determined at the MP2/6-31G* level are, (BN) 1.430 angstrom, (BH) 1.197 angstrom, (NH) 1.012 angstrom, (BNB) 122.9-degrees and (NBN) 117.1-degrees. HF-SCF and MP2/6-31G* vibrational frequencies have been calculated in the harmonic approximation and the vibrational spectrum of borazine is reassigned accordingly.