DFT Study of Polymorphism in Al(OH)3: A Structural Synthon Approach |
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| Authors: | Supreeth Nagendran Ganga Periyasamy P. Vishnu Kamath |
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| Affiliation: | Department of Chemistry, Central College, Bangalore University, Bangalore 560 001, India |
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| Abstract: | All the known polymorphs of Al(OH)3 comprise a stacking of charge neutral layers having the composition [Al2/3□1/3(OH)2] (□: cation vacancy) and designated by the symbol P. Employing a single Al(OH)3 layer (layer group p121/a1) as a structural synthon, the energy profile computed for the translations of P and $bar{P}$ ($bar{P}$ : mirror image of P) layers relative to each other within a bilayer model, not only show minima corresponding to the four known polymorphs of Al(OH)3 but also predict three new polymorphs with energy minima at the stacking vectors (7/10, 5/18, 1) (polymorph B1), (1/2, 0, 1) (polymorph B2) and (2/5, 1/9, 1) (polymorph B4). Of these B1 and B2 are 0.30 eV and 0.23 eV below the energy of bayerite (B3), but 0.30 eV and 0.37 eV above the global minimum which corresponds to gibbsite. B4 is only 0.08 eV above the energy of bayerite. This quantitative structural synthon approach offers B1, B2, and B4 as legitimate targets for future synthetic efforts. |
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| Keywords: | Layered hydroxides Layer group Stacking vectors Polymorphs Aluminum |
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