Cation distribution and structure modelling of spinel solid solutions |
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| Authors: | B Lavina G Salviulo A Della Giusta |
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| Institution: | (1) Dipartimento di Mineralogia e Petrologia, Università di Padova, Corso Garibaldi 37, 35137, Padova, Italy Tel.: +39-49 8272032; Fax: +39-49-8272010 e-mail: barbara@dmp.unipd.it, IT |
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| Abstract: | This paper presents an improved generalisation of cation distribution determination based on an accurate fit of all crystal-chemical
parameters. Cations are assigned to the tetrahedral and octahedral sites of the structure according to their scattering power
and a set of bond distances optimised for spinel structure. A database of 295 spinels was prepared from the literature and
unpublished data. Selected compositions include the following cations: Mg2+, Al3+, Si4+, Ti4+, V3+, Cr3+, Mn2+, Mn3+, Fe2+, Fe3+, Co2+, Ni2+, Zn2+ and vacancies. Bond distance optimisation reveals a definite lengthening in tetrahedral distance when large amounts of Fe3+ or Ni2+ are present in the octahedral site. This means that these cations modify the octahedral angle and hence the shared octahedral
edge, causing an increase in the tetrahedral distance with respect to the size of the cations entering it. Some applications
to published data are discussed, showing the capacity and limitations of the method for calculating cation distribution, and
for identifying inconsistencies and inaccuracies in experimental data.
Received: 19 February 2001 / Accepted: 1 June 2001 |
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| Keywords: | Spinel Cation distribution Bond distances Structure modelling |
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