  By means of low-temperature expansions (LTEs), the nucleation free energy and
the precipitate interface free energy are expressed as functions of the
solubility limit for alloys which lead to the precipitation of a stoichiometric
L12 compound such as Al-Sc or Al-Zr alloys. Classical nucleation theory is then
used to obtain a simple expression of the nucleation rate whose validity is
demonstrated by a comparison with atomic simulations. LTEs also explain why
simple mean-field approximation like the Bragg-Williams approximation fails to
predict correct nucleation rates in such an ordering alloy.
