LIU Qi1, YIN Xin-ya2
(1. State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China;
2. Guizhou Minzu University, Guiyang 550025, China)
Abstract：Density functional calculation is used to estimate isotope fractionation factor between B(OH)3 and B(OH)4- in aqueous solution. A “Water-droplet” configuration based on molecular cluster model was chosen for simulating the aqueous environment where every “water-droplet” contains n∙H2O molecules (n=6, 12, 18, 24, 30) surrounding the molecule of interest. Our theoretical results show equilibrium isotope fractionation of boron isotope exchange between B(OH)3 and B(OH)4- is equal to 1.031 in pure water at 25˚C, which is in good agreement with experimental observation. Comparison of several configurations containing different number of H2O molecules shows that the 12-molecule water cluster is an economic and accurate model for predicting boron isotope fractionation. Moreover, we discuss a defect in previous study of calculation of the boron isotope fractionation factor and suggest a possibility of using the cluster model in future investigation of boron isotope fractionation during carbonate formations.
Key words：boron isotope; equilibrium isotope fractionation; quantum chemical calculation; aqueous solution
ACTA MINERALOGICA SINICA Vol. 34, No. 4, 2014, Page 535-541
