The self-diffusion coefficients of liquid binary M-Si (M=Al, Fe, Mg and Au) alloy systems by first principles molecular dynamics simulation

Through first-principles molecular dynamics simulation, the self-diffusion coefficients of five elements in the four liquid binary M-Si (M=Al,Fe,Mg,Au) alloy systems are obtained under the same overheating temperature. Except for DFe, the self-diffusion coefficient of the other four elements vary significantly with concentration of Si (cSi). The mixing enthalpy between Si and M elements determines the slop of DSi vs cSi curves in Si-rich range. The dominant factor on DSi is the partial coordination number of NSiSi: the larger the NSiSi is, the smaller DSi becomes. The secondary factor on DSi is the medium-range order in liquid alloys: the stronger the medium-range order is, the smaller DSi will be. Complex behavior of coupling or decoupling of self-diffusion coefficients in these liquid binary alloys are observed.