Short-range structural signature of excess specific heat and fragility of metallic-glass-forming supercooled liquids

Supercooled metallic liquids exhibit very different temperature (T) dependence of the excess specific heat (ΔC ^p) and viscosity, profoundly influencing their glass-forming ability. Using two model glass-forming liquids in molecular dynamics simulation, here we demonstrate that their contrasting ΔC ^p and relaxation/viscosity behavior has an underlying origin in their different T-dependent local structural ordering. Upon undercooling toward glass transition, a particularly stabilizing type of short-range ordering that accelerates with decreasing T leads to a steeply rising ΔC ^p and higher fragility, whereas local motifs that merely respond to the densification of the liquids result in a weak T dependence of ΔC ^p.