Local order and structural transitions in amorphous metal-metalloid alloys

The ${\mathrm{Ni}}_{80}$ ${\mathrm{P}}_{20}$ alloy system has been investigated in both liquid and amorphous solid forms using molecular-dynamics computer simulation. Atomic interactions were modeled by central pair potentials selected to represent roughly the atomic sizes and relative bond strengths. Self-diffusion constants and pair-correlation functions have been determined as a function of temperature. By means of a mass-weighted steepest descent on the potential-energy hypersurface, dynamical configurations at various temperatures have been mapped onto nearby potential-energy minima (stable atomic packings). This establishes that the liquid phase for the alloy has a temperature-independent inherent structure. Comparison with diffraction data on real Ni-P alloys suggests (and we verify) that improved molecular-dynamics modeling is possible.