The structure and thermodynamic properties of liquid Al–Si alloys by ab initio molecular dynamics simulation

• Three most frequent polyhedrons around Si atoms are nearly unchanged vs composition.
• The dissolution of Si particles was explained based on the structure of liquid Al−Si alloy.
• The calculated mixing enthalpy is much larger than what was employed in CALPHAD.

The structure and mixing enthalpy of liquid Al–Si alloys has been investigated by ab initio molecular dynamics simulation. It is found that the three most frequent Voronoi polyhedron around Si atoms are nearly unchanged as the Si composition decreases from pure Si to about 4 at.% Si. The robustness of local structure of Si atoms permits us to establish a model to describe the dissolution behavior of Si particles into liquid Al, in which the structure of interface between liquid Al and Si particle might be like that of liquid pure Si, and hence the dissolution of Si particles should be interfacial reaction controlled. Some previous observations related to Al–Si alloys may be well understood based on this model. The calculated mixing enthalpy has a maximum of about − 7 kJ/mol, which is much larger than what is used in the present phase diagram calculations.