Revisiting the structure–property relationship of metallic glasses: Common spatial correlation revealed as a hidden rule

What determines the glass property remains one of the major unsolved problems in both condensed matter physics and materials science. Despite extensive research attempting to identify possible structural features as property signatures in glasses obeying the conventional philosophy of “structure determines property” in matter, the hidden rule about why some proposed structures predict properties effectively but others do not is still poorly understood. Here we revisit some earlier proposed successful “structural descriptors” in glasses, e.g., vibrational mean-squared displacement, flexibility volume, participation fraction of low-frequency vibrational modes, and two-body excess entropy, correlating them with the long-time dynamic property of model glass probed via the activation energy for local structural excitation. We find that all four structural descriptors correlate strongly with the activation energy, presenting large Pearson's correlation coefficients. By examining the spatial nature of the activation energy and the structural descriptors, a common rule for the robustness of structure–property relationships in glasses is established, according to which there exists a critical characteristic correlation length. We further demonstrate the concept that complex structures determine the glass property by manipulating the cutoff distance used to define the two-body excess entropy. Only if this structural descriptor is defined involving atoms beyond the first nearest neighbor does it reproduce the feature of common spatial correlation range in glass. The presence of a common spatial correlation length strongly indicates that it is necessary to include the spatial correlation of a complex structure accounting for the dynamic property of metallic glasses.