Computational investigations of symmetry and coupled substitutions in natrolite group minerals | Szegedi Tudományegyetem, Ásványtani, Geokémiai és Kőzettani Tanszék

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Mai névnapok:

Emil, Csanád

Computational investigations of symmetry and coupled substitutions in natrolite group minerals

Reference:
Acta Mineralogica-Petrographica, Szeged 2004, Vol. 45/1, pp. 113–117

Szerző:
Váczi Tamás
Michele C. Warren

Abstract:
Empirical interatomic potentials and energy minimisation techniques were used to test atomic configurations of two minerals of the NAT zeolite topology, natrolite and gonnardite. The natrolite structure (Artioli et al., 1984) was found not to be stable in the empirical Fdd2 space group. With symmetry constraints released during minimisation, the structure relaxed either with a slight triclinic distortion or to an unphysical configuration, though intermediate steps during minimisation showed first monoclinic and later triclinic symmetry. In the gonnardite structure (Artioli and Torres Salvador, 1991), simulations with full cation disorder but only some of the extraframework water molecules included showed a positive correlation between the cell parameters and Ca content. Since the averaging of potentials does not properly represent disorder in extraframework and coupled sites, we instead built a model structure with full order in extraframework cation sites and the proper number of water molecules. Energetically favourable locations for H2O molecules relative to Ca atoms were found only in the latter model.

 

Letöltés

 

acta2004, disorder, energy minimisation, gonnardite, natrolite

 

 




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