Correlation between mixing enthalpy and structural order in liquid Mg-Si system
(1. Shandong Provincial Key Laboratory of High Strength Lightweight Metallic Materials, Advanced Materials Institute, Qilu University of Technology (Shandong Academy of Sciences), Ji’nan 250014, China;
2. Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Ji’nan 250061, China;
3. School of Materials Science and Engineering, Liaocheng University, Liaocheng 252000, China;
4. Ulsan Ship and Ocean College, Ludong University, Yantai 264025, China;
5. School of Mathematics and Physics, Qingdao University of Science and Technology, Qingdao 266061, China)
2. Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Ji’nan 250061, China;
3. School of Materials Science and Engineering, Liaocheng University, Liaocheng 252000, China;
4. Ulsan Ship and Ocean College, Ludong University, Yantai 264025, China;
5. School of Mathematics and Physics, Qingdao University of Science and Technology, Qingdao 266061, China)
Abstract: The mixing enthalpies and structural order in liquid Mg-Si system were investigated via ab-initio molecular dynamics at 1773 K. By calculating the transferred charges and electron density differences, the dominance of Si-Si interactions in the chemical environments around Si was demonstrated, which determined that the mixing enthalpy reached the minimum on Mg-rich side. In terms of Honeycutt and Anderson (HA) bond pairs based on the partial pair correlation functions, the attraction between Si-Si pairs and Mg atoms was revealed, and the evolution of structural order with Si content was characterized as a process of constituting frame structures by Si-Si pairs that dispersed Mg atoms. Focusing on tetrahedral order of local Si-configurations, a correlation between the mixing enthalpy and structural order was uncovered ultimately, which provided a new perspective combining the energetics with geometry to understand the liquid Mg-Si binary system.
Key words: liquid Mg-Si system; mixing enthalpy; structural order; ab-initio molecular dynamics