Study of local density fluctuations in liquid and amorphous iron using molecular dynamics simulation

We have studied dynamics in the liquid and amorphous Fe by means of molecular dynamics (MD) simulation. A series of MD models containing 10(4) particles under periodic boundary conditions are prepared at temperatures from 290 K to 2250 K. It was shown that the second peak of the radial distribution function (RDF) appears to split when the liquid transforms to an amorphous solid. Further, we focus on local density fluctuations (LDF) which happen in simulated samples. We found that LDFs operate as a diffusion vehicle. The diffusion is performed by two types of LDFs. As the temperature decreases, LDFs are strongly correlated so that the fraction of I-type LDFs increases and the spatial distribution of LDFs is heterogeneous. We propose a new model for diffusion in liquid and amorphous solids which gives new insight into the dynamics slowdown below the melting point and diffusion mechanism in amorphous materials.