Infinitely rugged intra-cage potential energy landscape in metallic glasses caused by many-body interaction

The absence of translational symmetry in glassy materials poses a significant challenge in establishing effective structure-property relationships in real space. Consequently, the potential energy landscape (PEL) in phase space is widely utilized to comprehend the complex phenomena in glasses. The classical PEL features a two-scale profile comprising mega-basins and sub-basins, corresponding to α-relaxations (e.g. glass transition) and β-relaxations (e.g. local cage-breaking atomic rearrangements), respectively. Recent studies, however, reveal that sub-basins are not smooth and contain finer structures, the origins of which remain elusive. Here we probe the smoothness of sub-basin bottoms in glasses' PEL by introducing small intra-cage cyclic loading and then measuring the net changes in atomic-level stresses. Compared to glasses with pair interaction, glasses with many-body interaction exhibit orders-of-magnitude larger and loading-dependent stress changes even before the first cage-breaking event takes place, which reflect much more feature-rich sub-basins. We further demonstrate this stark contrast stems from the spatial distribution of individual atom's constraining force field. Specifically, at vanishing perturbations, many-body interactions disrupt the positive-definite synchrony in energy variations of the perturbed atom and the whole system, causing inherently less confined atomic responses and infinitely rugged sub-basins. The implications of these findings for the selective addition or removal of fine structures in the PEL and the subsequent tuning of glassy materials' responses to external stimuli are also explored.

玻璃态材料中平移对称性的缺失对在实空间建立有效的结构 - 性能关系构成了重大挑战。因此，相空间中的势能面（PEL）被广泛用于理解玻璃中的复杂现象。经典的势能面具有包含巨盆地和子盆地的双尺度轮廓，它们分别对应于α弛豫（例如玻璃化转变）和β弛豫（例如局部笼破缺原子重排）。然而，近期研究表明，子盆地并不平滑，且包含更精细的结构，其起源仍然难以捉摸。在此，我们通过引入小的笼内循环加载，然后测量原子级应力的净变化，来探究玻璃势能面子盆地底部的平滑性。与具有成对相互作用的玻璃相比，具有多体相互作用的玻璃甚至在首次笼破缺事件发生之前，就表现出数量级更大且与加载相关的应力变化，这反映出子盆地具有丰富得多的特征。我们进一步证明，这种鲜明的对比源于单个原子约束力场的空间分布。具体而言，在微小扰动下，多体相互作用破坏了受扰原子和整个系统能量变化的正定同步性，导致原子响应的固有约束更小以及子盆地极其崎岖。还探讨了这些发现对势能面中精细结构的选择性添加或去除以及随后对玻璃态材料对外界刺激响应的调控的影响。