中文摘要：

采用密度泛函方法模拟了阳离子对水体中B（OH）3和B（OH）4-的影响,计算海水的硼同位素平衡分馏参数。模拟海水环境时,选择基于分子簇模型的＂水滴＂法,以最多12个水分子环绕兴趣分子的方式构建＂水滴＂。对海水环境的计算结果显示,B（OH）3和B（OH）4-的硼同位素平衡分馏系数在25？C时为1.031,与纯水环境下的该分馏值并无明显差别。研究表明前人对B（OH）3和B（OH）4-间硼同位素平衡分馏参数的实验测定可能存在问题。研究结果为精进硼同位素古环境重建工作和硼同位素平衡分馏测定提供了理论制约。

英文摘要：

Density functional method is used to simulate effects from cations for calculating isotope fractionation factor between B（OH）3 and B（OH）4- in seawater. ＂Water-droplet＂ configuration based on molecular cluster model is chosen for simulating seawater environment, and up to 12 water molecules are used to surround the interested molecules in ＂water-droplets＂. This study shows equilibrium isotope fractionation factor between B（OH）3 and B（OH）4- is 1.031 in seawater at 25？C, which is similar to the fractionation factor in pure water. Our results show that there may be improprieties in previous experimental observation of boron isotope fractionation in solution, and provide theoretical constrains for better constructing paleo-environments by boron isotope proxy and better measuring equilibrated boron isotope fractionation in solution.