PERIODIC HARTREE-FOCK CALCULATION OF THE A(1G) (T-Z) AND E-G (T-X, T-Y) PHONON MODES IN ICE-VIII

The raman active phonon modes A(1g) (T-z) and E-g (T-x, T-y) of ice VI II have been calculated at the periodic Hartree-Fock level for a selec tion of cell volumes covering the 0-30 GPa pressure range. The calcula tion correctly reproduces the frequencies as well as their pressure de rivatives. These phonon modes correspond to the relative displacement of the two hydrogen bonded sublattices of ice VIII and are therefore a reliable probe to investigate the part of the intermolecular potentia l which does not depend upon the hydrogen bond formation. These result s which complement those of previous calculations on ice VIII, bring a dditional support for the reliability of the Hartree-Fock scheme in th e study of ice modifications. (C) 1997 Elsevier Science B.V.