Ab initio molecular dynamics simulation and free energy exploration of copper(I) complexation by chloride and bisulfide in hydrothermal fluids
Ab initio molecular dynamics simulation and free energy exploration of copper(I) complexation by chloride and bisulfide in hydrothermal fluids
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DOI：
10.1016/j.gca.2012.10.027
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发表时间：
2013-02
影响因子：
5
通讯作者：
Y. Mei;D. Sherman;Weihua Liu;J. Brugger;J. Brugger
中科院分区：
文献类型：
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作者：
Y. Mei;D. Sherman;Weihua Liu;J. Brugger;J. Brugger
氯化物和二硫化物被认为是控制铜在热液流体中迁移的主要配体。采用基于密度泛函理论的从头算分子动力学（MD）模拟方法，预测了室温、327°C和500 bar条件下，氯和硫氢化物（HS−和H2S（aq））混合流体中Cu（I）配合物的化学计量和几何构型，并评估了氯和硫氢化物配体对Cu输运的相对重要性.模拟准确地再现身份和几何形状的氯化铜（I）和二硫化物物种来自实验的溶解度，紫外-可见光谱，并在原位XAS结果。模拟结果表明，Cu（I）络合物的配体偏好如下：HS−>Cl−>H2S，但预测混合配体络合物CuCl（HS）−的稳定性很高，这是一种类似于Zajacz等人（2011）提出的NaClCuHS气相物种。采用距离约束分子动力学模拟方法，采用热力学积分方法，研究了Cu（I）氯化物和二硫化物配合物的热力学性质（形成常数，logKs）.以下反应的预测logKs与实验值（Brugger等人，2007; Liu等人，（2001年）：预测的logK与实验数据之间的一致性表明，通过MD模拟预测过渡金属配合物在水热条件下的热力学性质具有潜力。首次计算了混合配体络合物CuCl（HS）−的形成常数：确定Cu（I）络合物的形成常数使得能够完全基于MD模拟数据构建活度-活度图。结果表明，混合配体配合物在热液流体中铜的迁移过程中起着重要作用。
Chloride and bisulfide are the primary ligands believed to control the transport of copper in hydrothermal fluids. Ab initio molecular dynamics (MD) simulations based on density functional theory were conducted to predict the stoichiometries and geometries of Cu(I) complexes in mixed chloride and hydrosulfide (HS−and H2S(aq)) fluids at ambient temperature and at 327°C and 500bar, and to assess the relative importance of the chloride and hydrosulfide ligands for Cu transport. The simulations accurately reproduce the identity and geometries of Cu(I) chloride and bisulfide species derived from experimental solubility, UV–Vis, and in situ XAS results. The simulations indicate the following ligand preference: HS−>Cl−>H2S for Cu(I) complexes, but predict a high stability of the mixed-ligand complex, CuCl(HS)−, a species similar to NaClCuHS species in vapour phase suggested by Zajacz et al. (2011). The thermodynamic properties (formation constants, logKs) of Cu(I) chloride and bisulfide complexes were investigated by distance-constrained MD simulations using thermodynamic integration. The predicted logKs of the following reactions are in good agreement (within 1log unit) with the experimental values (Brugger et al., 2007; Liu et al., 2001): The fair agreements between the predicted logKs with those derived from experimental data demonstrate the potential of predicting thermodynamic properties for transition metal complexes under hydrothermal conditions by MD simulations. The formation constant for the mixed-ligand complex CuCl(HS)−is calculated for the first time: Determination of the formation constants for Cu(I) complexes enabled the construction of activity–activity diagrams entirely based on the MD simulation data. The results suggest that the mixed-ligand complex plays an important role in Cu transport in hydrothermal fluids.