Correlation between mixing enthalpy and structural order in liquid Mg−Si system

液态Mg−Si系中混合焓与结构序之间的相关性

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.

采用第一性原理分子动力学研究1773 K下液态Mg−Si系的混合焓与结构序。通过计算转移电荷和差分电子密度,证实Si原子周围的化学环境由Si−Si相互作用所主导,由此决定混合焓在富Mg侧达到最小值。基于偏偶相关函数的HA键对分析结果显示,Si−Si原子对与Mg原子相吸引,且结构序随Si含量的演变可以描述为Si−Si原子对分散Mg原子以构成框架结构的过程。以局域Si原子构型的四面体序为研究对象,揭示混合焓与结构序之间的相关性,这能为理解液态Mg−Si二元系提供综合能量学与几何学的新视角。