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Page 2 of 12 Liu et al. J Mater Inf 2022;2:20 https://dx.doi.org/10.20517/jmi.2022.29

INTRODUCTION
High-entropy metallic glasses (HEMGs) are the conceptual combination of high entropy alloys (HEAs) and
MGs. HEMGs are amorphous alloys in nature, without long-range translational symmetry. Meanwhile,
HEMGs have the (near) equiatomic composition containing at least five elements, leading to a high
configuration entropy of mixing. For HEAs, the most distinguishing characteristics are high entropy,
[1]
sluggish diffusion, and cocktail effects . However, it is unclear whether HEMGs will derive these traits from
such special compositions. Many studies have reported that HEMGs possess enhanced electrocatalytic
[4]
[6]
[2,3]
[5]
activity , excellent irradiation tolerance , superior cytocompatibility , and thermoplastic formability ,
which indicates that HEMGs have great potential for application.
Understanding the mechanical behaviors and deformation mechanisms of MGs has always been a hugely
significant and challenging issue in materials science. Extensive experiment and simulation results
[7-9]
demonstrate that they are associated with nanoscale heterogeneity . The local plastic deformation of MGs
is accommodated by flow units or referred to as “defects”. However, how to identify these “defects” from the
structural and/or dynamic features is still open to discussion. On one hand, the structural descriptors
[10]
attempt to distinguish the “defects” based on atomic packing, including free volume , quasi-punctual
[14]
[11]
[13]
[12]
defects , local fivefold symmetry (LFFS) , geometrical unfavored motif , Q parameter , and so on. On
k
the other hand, the dynamic descriptors stress the active response to external stimulus, and hence the
“defects” may be measured by soft mode [15,16] and vibrational mean squared displacement [17,18] . Compared
[19,20]
with conventional single/double element-based MGs, HEMGs show ultrahigh strength and enhanced
[4]
intrinsic ductility . A series of research on creep reported that HEMGs have a smaller serration during
[21] [19,22,23] [22]
plastic flow , a smaller apparent activation volume , and a slower annihilation of free volume , than
conventional MGs. Such a mechanical behavior of HEMGs is interpreted by a more homogeneous atomic
[24,25] [24]
arrangement with less loose packing “defects” , from the structural perspective, and it is also caused by
the sluggish atomic diffusion [20,26] and the inactive response of atomic motion to stress [19,26] , in the view of
dynamics. However, the evidence and understanding of heterogeneity at the atomic level are rare, which
attracts our interest in unfolding the atomic mechanism of stress-induced heterogeneity in HEMGs.
Applying MD simulations and ML techniques, pioneering work proposed several machine-learned
[27] [28] [29] [30]
“defects”, such as softness , quench-in softness , structural flexibility , atomic-scale stiffness , and
[31]
integrated glassy defect . However, these machine-learned “defects” either only involve atomic packing
without dynamics or fail in high-load/temperature conditions. This paper intended to characterize the
stress-induced heterogeneity in HEMGs from learning atomic dynamics. We generated the atomic
trajectories under thermal and mechanical stimuli by MD simulation, and then we used the k-nearest
neighbors (kNN) ML model to quantitatively predict how an atom responds to external stimuli. According
to the predicted T , liquid-like atoms (LAs) and solid-like atoms (SAs) can be defined accordingly. The
ML
results will reveal the correlation between liquid-like “defects”, local plasticity, atomic packing symmetry,
and chemical ordering.

MATERIALS AND METHODS
Classical MD simulation
Sample model preparation
As Takeuchi et al. synthesized by experiment, we prepared a Cu Zr Ni Ti Pd alloy model containing
20
20
20
20
[32]
20 3
50,000 atoms . The simulation box had a dimension of ca. 10 × 10 × 10 nm , and every dimension was
subjected to the periodic boundary condition. The atomic interactions were computed by the
[33]
embedded-atom method potential . The amorphous structure was obtained by melting and equilibrating
at 2000 K and zero pressure for 500 ps and then quenching to desired temperatures at a cooling rate of