Hydration of Sr2+ in hydrothermal solutions from ab initio molecular dynamics

Ab initio molecular dynamics calculations have been used to study the dynamical properties of the strontium hydration shell as a function of temperature. At 25 degreesC, we obtained Sr-O bond lengths of 2.6 Angstrom and a coordination number of 7.5. These are in good agreement with available experimental data. Increasing the temperature to 350 degreesC led to a decrease in the coordination number to 6.7 and a contraction of the first shell by about 0.1 Angstrom. This is in agreement with the data which predict octahedral coordination of Sr in water at high temperatures. Our calculated Debye-Waller factors also agree well with the experimental values. At higher temperatures (600 degreesC), we predict that the Sr ion remains in 6-fold coordination.