基于密度泛函理论研究六价铬的形态及其相互转变规律

Speciation and Its Mutual Transformation of Hexavalent Chromium Based on Density Functional Theory

为了研究六价铬在水溶液中的形态及其相互转变规律,用密度泛函理论中的B3LYP方法对H_2CrO_4、HCrO_4^-、Cr_2O_7^(2-)、CrO_4^(2-)进行结构优化,并在相同计算水平下对频率进行计算,其中对Cr采用基组为cc-pVDZ,而其它原子采用6-311+G(d,p)基组。通过静电势分析、原子电荷分析以及热力学分析表明溶液中氢离子与六价铬的结合能力由小到大为H_2CrO_4<HCrO_4^-<Cr_2O_7^(2-)<CrO_4^(2-)且Cr_2O_7^(2-)主要以重铬酸盐形式存在于固相中,而在溶液中六价铬主要以CrO42-的形式存在。而H_2CrO_4与HCrO_4^-在溶液中的存在较少。

To study the speciation and mutual transformation of hexavalent chromium in aqueous solution,the structures of H2CrO4,HCrO4^-,Cr2O7^2-and CrO42-were optimized by B3 LYP method of density functional theory,and the frequency was calculated at the same level. The basic group cc-pVDZ was used for Cr,while the otheratoms were under 6-311 ＋ G（d,p）. The analysis of atomic charge,electrostatic potential and thermodynamicenergy showed that the binding capacity between hydrogen ions and hexavalent chromium in the solutionincreased in the order of H2CrO4HCrO4^-Cr2O7^2-CrO42-. And Cr2O7^2-mainly presented in the form of dichromatein the solid phase,while most of hexavalent chromium in solution presented in the form of CrO42-,less in the form of H2CrO4 or HCrO4^-.