Ion specific effects on the structure of molten AF-ZrF systems (A = Li, Na, and K)

Pauvert, O.*; Salanne, M.*; Zanghi, D.*; Simon, C.*; Reguer, S.*; Thiaudire, D.*; Okamoto, Yoshihiro; Matsuura, Haruaki*; Bessada, C.*

Journal of Physical Chemistry B, 115(29), p.9160 - 9167, 2011/07

https://doi.org/10.1021/jp203137h

The structure of molten AF-ZrF system (A=Li, Na, K) is studied using EXAFS spectroscopy with molecular dynamics simulations. From the Zr solvation shell point of view, we observe a progressive stabilization of the 7-fold and then of the 6-fold coordinated complexes when passing from Li to Na and K as a "counterion". Particular attention is given to the systems consisting of 35 mol% of ZrF. At that particular composition, the ZrF complex predominates largely whatever the nature of the alkali. The calculated vibrational properties of this complex are in excellent agreement with a previous Raman spectroscopy experiment on molten KF-ZrF. The most important differences are observed for the lifetime of these octahedral units. On a larger scale, an intense first sharp diffraction peak is observed for the Zr-Zr partial structure factor, which can be attributed to the correlations between the octahedral units formed.