Ab initio calculation of conformation and vibrational spectrum for the pyrosulfate ion

Theoretical calculations have been performed and applied to determine the most likely geometry for the pyrosulfate ion. The main question was to determine as to whether the system has C2 or C2v conformation. The present study favors C2 symmetry. Bond lengths and angles have been calculated for the isolated ion, and the results compare well with experimental results for the ion in solid-state salts. Also, the vibrational spectrum of the S2O72- ion has been calculated and compared with experimental results, obtained by extrapolation from Raman spectra of salt melts of M2S2O7, M = Na, K, Rb, and Cs.