Study on Decomposition Mechanism of K3AlF6 by Quantum Chemical Calculations

• Published in: Russian Journal of Physical Chemistry A 2023-05, Vol.97 (5), p.997-1006
• Main Authors: Zhang, Yifan, Hu, Xianwei, Zhang, Wendi, Yang, Jiaxin, Chen, Liyu, Tang, Shuai, Liu, Aimin, Shi, Zhongning, Wang, Zhaowen
• Format: Article
• Language: English
• Subjects: Chemistry; Chemistry and Materials Science; Decomposition reactions; Density functional theory; Mathematical analysis; Physical Chemistry; Quantum chemistry; Raman spectra; Rate constants; Structure of Matter and Quantum Chemistry
• ISSN: 0036-0244; 1531-863X
• DOI: 10.1134/S0036024423050308

The decomposition mechanism of K 3 AlF 6 was investigated by quantum chemical calculation based on density functional theory (DFT). In order to clarify the structure properties of the optimized K 3 AlF 6 , the Mayer bond order (MBO) was systematically calculated. Two dissociation paths of K 3 AlF 6 were determined, meanwhile, trigonal bipyramidal and tetragonal pyramidal structures of [AlF 5 ] 2– complex ions were verified during the decomposition of K 3 AlF 6 . Furthermore, based on the data of calculated rate constants within a temperature range of 498–1473 K at canonical variational theory (CVT), it was thought that the decomposition reaction R1 involving Al2-F4/F7/F8 bond ruptures contributed much more to the decomposition of K 3 AlF 6 . Moreover, the calculated Raman spectrum of [AlF 5 ] 2– was close to the experimental spectrum. According to the analysis on the decomposition mechanism of K 3 AlF 6 and theoretical Raman spectra, the trigonal bipyramidal structure of [AlF 5 ] 2– complex has been proved to be the main product in the dissociation reaction of K 3 AlF 6 .