Quantitative relations between nearest-neighbor persistence and slow heterogeneous dynamics in supercooled liquids

Area of Science:

• Condensed Matter Physics
• Materials Science
• Computational Chemistry

Background:

• Glass-forming liquids exhibit complex dynamics near the glass transition.
• Understanding particle rearrangements and persistence is crucial for characterizing these dynamics.
• Conventional relaxation metrics like the self-intermediate scattering function capture some aspects of these dynamics.

Purpose of the Study:

• To investigate the decay of the normalized neighbor-persistence function, CB(t), in glass-forming liquids.
• To compare CB(t) with other established relaxation metrics.
• To analyze the temperature dependence of characteristic timescales associated with CB(t) and its relation to heterogeneous dynamics.

Main Methods:

• Molecular dynamics simulations of a binary Lennard-Jones model of glass-forming liquids.
• Analysis of the normalized neighbor-persistence function CB(t) decay.
• Fitting CB(t) to a double-stretched-exponential functional form.
• Comparison of timescales: bond lifetime (τbond), alpha-relaxation time (τα), overlap time (τov), and immobile-particle cluster lifetime (τimm).

Main Results:

• CB(t) decay follows a double-stretched-exponential form in the non-Arrhenius regime, similar to S(q, t).
• The ratio τbond/τα exhibits non-monotonic temperature dependence, peaking at a crossover temperature Tx.
• τbond remains comparable to τov, and susceptibility peak time τχ remains comparable to τimm, despite large variations in these timescales.

Conclusions:

• CB(t) provides a valuable measure for characterizing the slow dynamics of glass-forming liquids.
• The relationship between τbond and τα offers insights into the heterogeneous dynamics near the glass transition.
• CB(t) and associated susceptibility χB(t) serve as semi-quantitative, spatially-averaged indicators of immobile-particle cluster dynamics.