- On the basis of a nonempirical pair potential, the temperature dependencies of the long-range-order parameter of NiTi and AuPd are calculated. The suggested effective potential approach allows one to describe the changes in phase relations. The evaluation of the internal mixing energy of alloys is carried out in the framework of the static concentration waves theory of Khachaturyan. The model outlines the technique to calculate the values of the energy parameters of the ordering process from first principles. © 1996 John Wiley & Sons, Inc.