Studies by Molecular Dynamics Simulations for Structure of Liquid Gallium at Ambient Pressure
|關鍵字:||液態鎵;靜態結構因子;Static structure factor;Liquid Ga|
Liquid Ga at ambient pressure (AP) is well known for its anomalous static structure factor (SSF), which displays a shoulder on the high-q side of its first peak. Since the experimental observation for liquid Ga nearly half a century ago, the physical cause for the high-q shoulder in the SSF has been a long-standing issue in liquid metal research. In this thesis, the structure of liquid Ga at AP were studied by using classical and ab initio molecular dynamics (MD) simulations. Loose pack structures with low coordination numbers were found in liquids generated by both MD simulations. To explore the local structures of the simulated liquids, a cluster approach defined by using the local bond-orinetational order (LBOO) parameters was developed. With common analyzed results, two types of LBOO clusters were found in liquids obtained by both MD simulations. One type of the clusters is characterized by sixfold orientational symmetry and their cluster SSFs are akin to that of a hard-sphere fluid. The other type of the clusters is typified by fourfold orientational symmetry and their cluster SSFs generally display an asymmetric first peak, and even a high-q shoulder as the clusters are in highly LBOO. Therefore, the two types of LBOO clusters play contrasting roles for the appearance of the high-q shoulder in the SSF of liquid Ga. The local structures of particles with low coordination numbers are favorable to LBOO with fourfold orientational symmetry, so it is confirmed that the anomalous SSF of liquid Ga is related to the structures caused by particles with low coordination numbers. On the other hand, the similarity between the local structures of the LBOO clusters and the structures of multiple Ga solids were examined. According to the ab initio MD simulations, the cluster structures with fourfold orientational symmetry have a tendency to resemble more to the structure of β-Ga.