成矿流体中稀土离子配合物稳定性的第一性原理研究

Rare Earth Element (REE) has been applied to every area of national economy due to their excellent performance. The research and prospection of REE mineral resources is significant to the economic developments. The migration and enrichment mechanism of REE in ore-forming fluid is valuable by providing the basis for exploring the rare earth deposit. Previous experimental works show that F-, Cl-, and CO32- anions form stable complexes with REE ions. These anions play a key role in the migration and enrichment of REE. However, the order of relative stability of these complex under high T-P conditions is not clear. We plan to study the stability of cerium and yttrium complex in ore-forming fluids with first principle molecular dynamic simulation: Firstly, first principle methods are used to simulate the stepwise hydrolysis reactions of Ce(III), Ce(IV) and Y(III), and constrained molecular dynamic is used to calculate the acidity. Secondly, different models for Ce3+, Ce4+,Y3+ and F-, Cl-, CO32- complexes are built and metadynamic method is used to study the dissociation reactions of these complexes. On the basis of the simulation results, the influence of temperature, pressure and pH condition to the stability of cerium complex is discussed. Through this study, the stabilities of cerium and yttrium complex with F-, Cl-, and CO32- are revealed from theoretical calculation. It is expected the results of our study will help understanding the migration and enrichment mechanism of REE.

稀土元素因其自身优异的性能，大量应用于国民经济的各个领域。稀土矿产资源的探寻与我国经济发展密切相关。稀土元素在成矿流体中的迁移和富集规律为稀土矿床的探寻提供依据，具有重要研究价值。已有实验表明成矿流体中F-、Cl-、CO32-等离子和稀土离子形成稳定的配合物，对稀土的迁移和富集起重要作用。但高温高压条件下，稀土离子与这些阴离子的配合物稳定性仍然不够清楚。申请者拟使用第一性原理量子分子动力学模拟，研究成矿流体中铈离子和钇离子配合物的稳定性：首先，模拟在高温高压条件下Ce3+、Ce4+和Y3+的逐级水解过程，用约束分子动力学计算酸度系数；其次，分别构建Ce3+、Ce4+和Y3+与F-、Cl-、CO32-的配合物模型，用亚动态模拟研究配合物解离过程，计算稳定性常数，探讨温度压力和pH对配合物稳定性的影响。本研究预计可从计算角度揭示成矿流体中典型轻重稀土离子与F-、Cl-、CO32-配合物的稳定性，为探明稀土离子的迁移富集规律提供理论依据。