Existence of Al2F-7^- in molten MF–AlF3(M = K, Cs) systems as determined by Raman spectroscopy and structural simulation  

作　　者：Ming Lin Xianwei Hu Zhongning Shi Bingliang Gao Jiangyu Yu Zhaowen Wang 

机构地区：[1]School of Metallurgy,Northeastern University,Shenyang 110819,Liaoning,China [2]Key Laboratory for Ecological Metallurgy of Multimetallic Minerals,Ministry of Education,Shenyang 110819,Liaoning,China

出　　处：《Journal of Energy Chemistry》2020年第5期19-23,共5页能源化学（英文版）

基　　金：the National Natural Science Foundation of China(grant no.51474060);the National Key R&D Program of China(grant no.2017 YFC0805100);the National Natural Science Foundation of Liaoning Province(China)(grant no.2019-MS-129);the Fundamental Research Funds for the Central Universities of China(grant no.N162502002).

摘　　要：The molten mixtures of alkali metal fluorides and aluminum fluoride are applied as aluminum electrolytes or brazing fluxes.However,the presence of Al2F-7^-in such molten systems is disputed.In the present study,MF-AlF3(M=K,Cs)systems with molar ratios<1 were studied by in-situ Raman spectroscopy and molecular simulation.The results show that,in addition to AlF6^(3-),AlF5^(2-),and AlF4^-,the systems also contained Al2F-7^-.The characteristic bands in the Raman spectra belonging to Al2F-7^-were located at about 225 cm^-1,315 cm^-1,479 cm^-1,and 720 cm^-1.There are two possible structures of Al2F-7^-,which belong to the D3d and D3hpoint groups.Both of these structures are linear,and their single-point energies were found to differ by only 0.31 kcal/mol.The molten mixtures of alkali metal fluorides and aluminum fluoride are applied as aluminum electrolytes or brazing fluxes. However, the presence of Al2F-7- in such molten systems is disputed. In the present study, MF–AlF3（M = K, Cs） systems with molar ratios < 1 were studied by in-situ Raman spectroscopy and molecular simulation. The results show that, in addition to AlF63-, AlF52-, and AlF4-, the systems also contained Al2F-7-. The characteristic bands in the Raman spectra belonging to Al2F-7- were located at about 225 cm-1, 315 cm-1, 479 cm-1, and 720 cm-1. There are two possible structures of Al2F-7-, which belong to the D3d and D3h point groups. Both of these structures are linear, and their single-point energies were found to differ by only 0.31 kcal/mol.

关 键 词：MF-AlF3(M=K Cs)systems Raman spectroscopy STRUCTURAL SIMULATION Al2F7^- Ionic structure 

分 类 号：TQ133.1[化学工程—无机化工] O657.37[理学—分析化学]