Vibrational frequencies and structural determination of hafnium tetrahydroborate

The normal mode frequencies and corresponding vibrational assignments of of hafnium tetrahydroborate in T symmetry are examined theoretically using the Gaussian 98 set of quantum chemistry codes. All normal modes were successfully assigned to one of to one of six types of motion (B-H stretch, Hf-B stretch, B-Hf-B bend, H-B-H bend, BH4 wag, and BH4 twist) predicted by a group theoretical analysis. By comparing the vibrational frequencies with IR and Raman spectra available in the literature, a set of scaling factors is derived. Theoretical IR and Raman intensities are reported. Quantum chemical calculations predict that the molecule does not possess strict Td symmetry. The Td structure possesses one negative eigenvalue. The minimum energy structure possesses T symmetry.