The phase diagrams of small particles (with diameters in the nm range) are
studied theoretically. In the Limit where thermodynamical arguments remain
valid, it is deduced that the phase diagram of small particles is a functio
n of their size. For the case of ideal solutions, it is shown that the lens
-shaped solidus-liquidus curves are shifted to lower temperatures when the
dimensions of the particle decrease. Additionally, at fixed temperatures be
tween the highest bulk melting point and the lowest melting point of the pa
rticle, the relative concentrations of the solid and Liquid phases are diff
erent in the particle and bulk material.