On the Use of Raman Spectra for MF + ZrF ₄ Molten Salts

A recent article in this Journal made incorrect conclusions regarding the bonding structure in molten salts of KF + ZrF₄ mixtures. Ab initio calculations (molecular dynamics simulations and Raman spectra predictions) are performed here with comparison to experiment. It is shown here that the vibrational frequency of the prominent Zr-F stretch mode (530-630 cm^-1) is an indicator of the number of <i>terminal</i> fluorides bound to the Zr atom, controlled predominantly by the mixing ratio. A chart relating this frequency to the number of terminal fluorides is provided.