Videographic reconstructions and simulations of the real Cu3Au structure at various temperatures

Abstract

Abstract Applying the videographic reconstruction and simulation method, the real domain structure configuration of the Cu3Au binary alloy is established at various temperatures. Starting from the partially-ordered state and varying the domain size (and shape), domain structures, interface type and the domain distribution in a disordered matrix, good agreement between the diffraction patterns (X-ray- and electron diffraction) and the videographic calculations is obtained. Both the reconstruction and the simulation results indicate that the gradual variation of the intensity distribution around the superlattice reflection positions arises from a domain-size distribution in a disordered matrix. The real structure of Cu3Au at 678 K, e.g., just above TC , is comprised of small 2-d domains with a certain size distribution (approx. 1–8 cells, small size preferred) and different shapes. The domains are almost randomly distributed in a disordered matrix and occasionally form an anti-phase relationship. They are separated by the disordered matrix and are not fully-ordered (short-range order). The matrix contains regions either deviating considerably from the average structure or resembling the average Cu3Au structure. The results obtained from the reconstruction using the random phase random amplitude model indicate that this model can be generally used as a starting model to “recover” the real structure in similar cases in which order/disorder phase transitions are present.