First-principles molecular dynamics investigation on Na3AlF6 molten salt

作者：Lv, Xiaojun; Xu, Zhenming; Li, Jie^*; Chen, Jiangan; Liu, Qingsheng

来源：Journal of Fluorine Chemistry, 2016, 185: 42-47.

DOI：10.1016/j.jfluchem.2016.03.004

• First-principles molecular dynamics
• Local structure
• Transport properties
• Na3AlF6
• Molten salt

Local structure and transport properties of Na3AlF6 molten salt were investigated by First-principles molecular dynamics (FPMD) simulation. For Na3AlF6 molten salt, the local ionic structure is governed by five-coordinated [AlF](2-) and six-coordinated [AlF6](3-). Coulomb force dominates the interionic interactions for Na3AlF6 molten salt. The first-shell average coordination number (CN) of Na-F, Al-F in the Na3AlF6 molten salt is 6.03, 5.45, respectively and the F-Al-F bond angles are mainly located at 87, 124 and 171. The percentage of bridging F-b is small about 1-2%, while the free F-f is up to 26%, suggesting the polymerization degree of local structure is lower. Al-F bonds of the [AlFx](3-x) groups in Na3AlF6 molten salt have ionic characters as well as partial covalent characters due to the hybridization of F-2p and Al-3s (3p) orbitals, while the Na-F and F-F bonds are mainly ionic. The order of ion diffusion ability was found as Ne+ > F- >Al3+. Calculated results of viscosity and ionic conductivity are in good agreement with the experimental results, generally within 7%.

• 出版日期2016-5
• 单位江西理工大学; 中南大学