Structure and Stability of the Al(OH)3 Polymorphs Doyleite and Nordstrandite: A Quantum Mechanical ab Initio Study with the CRYSTAL06 Code

Raffaella Demichelis*†, Michele Catti‡ and Roberto Dovesi†§
Dipartimento di Chimica IFM, Universit di Torino, Via Pietro Giuria 7, 10125 Torino, Italy, Dipartimento di Scienza dei Materiali, Universit di Milano Bicocca, Via Cozzi 53, 20125 Milano, Italy, and Nanostructured Interfaces and Surfaces (NIS), Centre of Excellence, Via Pietro Giuria 7, 10125 Torino, Italy
J. Phys. Chem. C, 2009, 113 (16), pp 6785–6791
DOI: 10.1021/jp810084c
Publication Date (Web): March 25, 2009
Copyright © 2009 American Chemical Society
* To whom correspondence should be addressed. Tel.: +39 011 670 7560. Fax: +39 011 670 7855. E-mail: raffaella.demichelis@unito.it., †

Universit di Torino.

, ‡

Universit di Milano Bicocca.

, §

NIS.

Abstract

The crystal structures and relative energies of doyleite and nordstrandite, two of the four aluminum trihydroxide polymorphs, were investigated at the periodic ab initio quantum-mechanical level with the CRYSTAL06 computer program, by using an all-electron Gaussian-type basis set and the hybrid B3LYP Hamiltonian. By least-energy optimizations of different starting arrangements of H atoms, a noncentrosymmetrical P1 structure model was proved to be slightly more stable than a P one in doyleite. The primitive P unit cell of nordstrandite was confirmed to contain four formula units, unlike doyleite (Z = 2). The layered structures of nordstrandite and doyleite were shown to be closely related to that of bayerite, differing from one another by the interlayer shift vectors only. From the optimized positions of H atoms, the hydrogen bonding schemes and geometries were fully determined for both polymorphs. The computed Gibbs free energies at 298 K of bayerite, doyleite, and nordstrandite, referred to that of gibbsite, are 3.9, 4.4, and 15.2 kJ mol−1 per formula unit, respectively. Nordstrandite was then predicted to be largely the less stable of all four Al(OH)3 polymorphs.

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History

  • Published In Issue April 23, 2009
  • Article ASAPMarch 25, 2009
  • Received: November 17, 2008
    Revised: January 16, 2009

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