  The effect of dopants on the metallic glass forming ability is usually
considered based on analysis of changes in the liquid structure or
thermodynamics. What is missing in such considerations is an analysis of how a
dopant changes the properties of the crystal phases which can form instead of
the glass. In order to illuminate this aspect we performed molecular dynamics
simulations to study the effects of Mg and Sm dopants on the crystal nucleation
in Al. The simulation data were found to be consistent with the experimental
observations that addition of Mg to Al does not lead to vitrification but
addition of only 8% Sm does. The significant effect of Sm doping was related to
the intolerance of Al to this dopant. This leads to increase in the
solid-liquid interfacial free energy, and therefore, to increase in the
nucleation barrier and to dramatic decrease in the nucleation rate. The
intolerance mechanism also significantly affects the growth kinetics.
