Fe2+/Fe3+ ordering in magnetite is described in terms of a simple mean-fiel
d approach based on an effective interionic Coulomb potential. It is shown
that first-order electronic order-disorder transformations, as reported in
the literature, can only be reproduced when the dependence of the interioni
c potential on the unit-cell dimensions is taken into account. In this case
the first-order transitions can then be viewed as the result of an interpl
ay between the lattice-deformation energy and the free-energy contribution
related to the electronic ordering of the octahedral Fe lattice. Furthermor
e, the effect of the lattice deformation by hydrostatic pressure on the Ver
wey transition can be successfully explained to some extent within the cont
ext of the same framework. In comparison to experimental data available fro
m the literature, the mean-field approach developed in this paper yields ve
ry acceptable results with respect to both qualitative and quantitative asp
ects, thus opening an interesting new viewpoint on the mechanism of the Ver
wey transition.