Strain energy density in the x-ray powder diffraction from mixed crystals and alloys

A correlation between precise x-ray powder diffraction patterns and atomic size mismatch in disordered mixed crystals (alloys and ionic crystals) is observed. The anisotropy of the elastic moduli has been taken into account for evaluation of the strain energy density of the mixed crystals revealed in x-ray powder diffraction measurements. The precursor of the phase transformation for a quenched disordered Au-Cu alloy is identified.