  The equilibrium short-range order (SRO) in Cu-Pd alloys is studied
theoretically. The evolution of the Fermi surface-related splitting of the
(110) diffuse intensity peak with changing temperature is examined. The results
are compared with experimental observations for electron-irradiated samples in
a steady state, for which the temperature dependence of the splitting was
previously found in the composition range from 20 to 28 at.% Pd. The
equilibrium state is studied by analysing available experimental and
theoretical results and using a recently proposed alpha-expansion theory of SRO
which is able to describe the temperature-dependent splitting. It is found that
the electronic-structure calculations in the framework of the
Korringa-Kohn-Rostoker coherent potential approximation overestimate the
experimental peak splitting. This discrepancy is attributed to the shift of the
intensity peaks with respect to the positions of the corresponding
reciprocal-space minima of the effective interatomic interaction towards the
(110) and equivalent positions. Combined with an assumption about monotonicity
of the temperature behaviour of the splitting, such shift implies an increase
of the splitting with increasing temperature for all compositions considered in
this study. The alpha-expansion calculations seem to confirm this conclusion.
