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Amphoteric behavior of hydrogen (H+1 and H-1) in complex hydrides from van der waals interaction included ab-initio calculation


In order to identify potential materials for hydrogen storage applications worldwide attention has been focused on hydrides with high gravimetric and volumetric capacity. Hydrogen is an unique element that possess positive, negative or neutral oxidation state in solids depending upon the chemical environment. Moreover, it is highly unusual to have hydrogen with both positive as well as negative oxidation state in the same structural framework and hence very few such compounds are reported in the literature based on structural study. If one can find hydrogen storage materials where hydrogen is present in both negative and positive oxidation state within the same structural framework then one can accommodate hydrogen with high volume density because of the attractive interaction between oppositely charged hydrogen. So, it is fundamentally as well as technologically important to identify compounds in which hydrogen is in amphoteric nature and understand the necessary criteria for its origin. The experimental structural analysis of Cyclotriborazane and Diammonium dodeca hydro–closo–dodecaborate with the chemical formula, (BH2NH2)3 and (NH4)2(B12H12), respectively insinuate the presence of partially charged hydrogen with anionic and cationic behavior within the same structure. In order to understand the role of van der Waals (vdW) interactions on structural parameters we have considered 12 different vdW corrected functionals for the structural optimization and found that the optPBE–vdW functional predict the equilibrium structural parameters reliably with less than 0.009 % deviation from experimental result. So, the optPBE–vdW functional is used to calculate charge density, electron localization function, total as well as partial density of state, Bader and Born effective charge etc. We have observed that hydrogen is exhibiting amphoteric behavior with H closer to B in the negatively charged state and that neighboring to N is in positively charged state.

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Publication details

The article was received on 04 Dec 2018, accepted on 10 Feb 2019 and first published on 12 Feb 2019

Article type: Paper
DOI: 10.1039/C8TA11685G
Citation: J. Mater. Chem. A, 2019, Accepted Manuscript

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    Amphoteric behavior of hydrogen (H+1 and H-1) in complex hydrides from van der waals interaction included ab-initio calculation

    K. Srinivasan, H. Fjellvåg and R. Ponniah, J. Mater. Chem. A, 2019, Accepted Manuscript , DOI: 10.1039/C8TA11685G

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