Evidence of Sharp Transitions between Octahedral and Capped Trigonal Prism States of the Solvation Shell of the Aqueous Fe3+ Ion

The structure of the solvation shell of the aqueous Fe3+ ion has been a subject of controversy due to discrepancies between experiments and different levels of theory. We address this issue by performing simulations for a wide range of ion concentrations, using various potential energy functions, su...

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Published inThe journal of physical chemistry letters Vol. 15; no. 17; pp. 4523 - 4530
Main Authors Goswami, Amrita, Peña-Torres, Alejandro, Jónsson, Elvar Ö., Egorov, Sergei A., Jónsson, Hannes
Format Journal Article
LanguageEnglish
Published American Chemical Society 02.05.2024
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ISSN1948-7185
1948-7185
DOI10.1021/acs.jpclett.4c00756

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Summary:The structure of the solvation shell of the aqueous Fe3+ ion has been a subject of controversy due to discrepancies between experiments and different levels of theory. We address this issue by performing simulations for a wide range of ion concentrations, using various potential energy functions, supplemented by density functional theory calculations of selected configurations. The solvation shell undergoes abrupt transitions between two states: a hexacoordinated octahedral (OH) state and a capped trigonal prism (CTP) state with 7-fold coordination. The lifetime of these states is dependent on concentration. In dilute FeCl3 solutions, the lifetimes of both are similar (≈1 ns). However, the lifetime of the OH state increases with ion concentration, while that of the CTP state decreases slightly. When a uniform negative background charge is used instead of explicit counterions, the lifetime of the OH state is greatly overestimated. These findings underscore the need for further experimental measurements and higher-level simulations.
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ISSN:1948-7185
1948-7185
DOI:10.1021/acs.jpclett.4c00756