Characteristic atom occupation patterns of Au3Cu, AuCu3, AuCuI and AuCuII based on experimental data of disordered alloys
(1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Powder Metallurgy Research Institute, Central South University, Changsha 410083, China;
3. State Key Laboratory for Powder Metallurgy, Central South University, Changsha 410083, China;
4. College of Mechanical Engineering, Xiangtan University, Xiangtan 411105, China)
2. Powder Metallurgy Research Institute, Central South University, Changsha 410083, China;
3. State Key Laboratory for Powder Metallurgy, Central South University, Changsha 410083, China;
4. College of Mechanical Engineering, Xiangtan University, Xiangtan 411105, China)
Abstract: The potential energies, volumes and electronic structures of characteristic atoms coordinated by neighboring configurations were obtained from the experimental heats of formation and lattice parameters of disordered Au1−xCux alloys. From characteristic atom occupation (CAO) patterns of L12-Au3Cu, L12-AuCu3 and L10-AuCu compounds, their electronic structures, volumetric and energetic properties were calculated. The CAO pattern of Johasson−Linde(J−L) model shows that the transition AuCuI→AuCuII is an exothermic and volume contraction reaction, which is opposite from experimental phenomena. According to CAO pattern of Guymont−Feutelais−Legendre(G−F−L) model, the AuCuII cell consists of two periodic antidirection (PAD) AuCuI regions and two PAD boundary regions. The equations derived from CAO pattern of G−F−L model can be used to calculate energetic properties, volumetric properties and ordering degrees of the PAD AuCuI region and PAD boundary region, as well as corresponding average properties of the AuCuII phase. The results are consistent with experimental phenomena.
Key words: Au-Cu system; intermetallics; electronic structure; crystalline structure; characteristic atom occupation pattern