铝电解质中碱金属阳离子对Al—O—F复合离子结构和稳定性的影响
Effect of alkali cations on structure and stability of aluminum-oxygen-fluorine complex ions in aluminum electrolytes
韩泽勋 1蒿鹏程 1陈长科 2陈润东 2张林威 2吕晓军1
作者信息
- 1. School of Metallurgy and Environment,Central South University,Changsha 410083,China
- 2. Xinjiang Joinworld Co.,Ltd,Urumchi 830000,China
- 折叠
摘要
铝电解质中复杂复合离子的结构和稳定性直接影响熔体的性质,进而影响铝电解过程及其技术经济指标.为此,本文采用密度泛函理论研究了碱金属阳离子对Al—O—F复合离子([Al2OF6]2−和[Al2O2F4]2−)的结构和稳定性的影响,分析其结构特征、电荷布居、拉曼光谱、阳离子结合自由能和态密度.研究表明,对于孤立的Al—O—F复合离子体系,[Al2OF6]2−复合离子的稳定性大于[Al2O2F4]2−复合离子;当加入碱金属阳离子后,较大尺寸的碱金属阳离子会增强[Al2OF6]2−和[Al2O2F4]2−复合离子的稳定性,这说明Al—O—F复合离子容易生成并长期存在于冰晶石熔盐电解质中,并遵循K3AlF6>Na3AlF6>Li3AlF6的顺序.从电子密度差图中可以直观地看到Al原子和碱金属阳离子的部分电荷消失后聚集到O和F原子周围.本文计算的Al—O—F复合离子的拉曼频率和文献值较为一致.
Abstract
In the aluminium electrolytes, the structure and stability of different complex ions directly determine the properties of the melts, and further affect the process and technical-economic indicator for aluminum electrolysis. Herein, we investigate the effect of alkali cations on structure and stability of aluminum-oxygen-fluorine complex ions ([Al2OF6]2− and [Al2O2F4]2−) using structural characteristics, charge population analysis, Raman spectrum, cationic binding free energy, density of state based on density functional theory calculation. The research indicates the [Al2OF6]2− ion is more stable than [Al2O2F4]2− ion for isolated Al—O—F ions. When adding the alkali cations, the cations with larger sizes enhance the stability of [Al2OF6]2− and [Al2O2F4]2− ions, implying the Al—O—F ions are easier to form and exist in cryolite electrolytes with a sequence of K3AlF6>Na3AlF6>Li3AlF6. We can observe intuitively the part of electrons of Al atoms and cation disappear and then gather around O and F atoms from electron density difference diagrams. The calculated Raman frequencies of the Al—O—F ions are greatly consistent with the published literature value.
关键词
Al—O—F复合离子/密度泛函理论/碱金属阳离子/铝电解质/结构和稳定性Key words
aluminum-oxygen-fluorine complex ions/density functional theory/alkali cations/aluminum electrolytes/structure and stability引用本文复制引用
基金项目
Innovation-Driven Project of Central South University,China(2016CX019)
National Natural Science Foundation of China(51674302)
出版年
2023
NETL
NSTL
维普
万方数据