A kinetic model for three-site intracrystalline ordering-disordering in minerals

Lian Kun Sha*, Bruce W. Chappell

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    3 Citations (Scopus)


    A kinetic model for describing the site occupancies of a cation at three nonequivalent sites in minerals has been presented as follows xi = ci0 + ci1eλ1t + ci2eλ2t (i = 1, 2, 3), where xi is the site occupancy of a given cation at site si , and ci0 (>0), ci1, ci2, λ1, and λ2 are constants at a given temperature and composition of the mineral. The two lemmas concerning three-site ordering-disordering indicate that λ1 and λ2 are either negative or complex-valued, and that they guarantee the convergence of the site occupancies with increasing time. The conditions for extrema have been given in the paper. The greatest difference between two-site and three-site order-disorder processes is that two-site ordering-disordering only occurs as either a monotonously increasing function or a monotonously decreasing function of time at a given initial total composition and temperature, while three-site order-disorder kinetics may have local minima or maxima.

    Original languageEnglish
    Pages (from-to)2075-2086
    Number of pages12
    JournalGeochimica et Cosmochimica Acta
    Issue number12
    Publication statusPublished - Jun 1996


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