Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session R20: Understanding Glasses and Disordered Matter Through Computational Models IFocus Live

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Sponsoring Units: DCOMP DSOFT GSNP DPOLY Chair: Pengfei Guan, Beijing Computational Science Res Ctr 
Thursday, March 18, 2021 8:00AM  8:36AM Live 
R20.00001: Acoustic probes for plasticity in amorphous materials Invited Speaker: Anne Tanguy Amorphous materials have a disordered structure inducing sound scattering and anomalous density of vibrations in the THz range. These properties affect their thermal properties, but also acoustic attenuation properties. These acoustic attenuation properties can be described in terms of an effective viscoelastic modelling for the constitutive laws charcterizing the material at the continuum scale. In the low frequency regime however, acoustic propagation is well described by plane waves and ballistic phonons. But the occurrence of plastic deformation results in a succession of local irreversible rearrangements at the nanometric scale known as Transformation Zones. These Transformation Zones are shown to be well described within the theory of Eshelby inclusions, and thus act as acoustic scatterers. We will discuss in this talk the signature of plasticity in acoustic scattering in amorphous materials. 
Thursday, March 18, 2021 8:36AM  8:48AM Live 
R20.00002: Atomic nonaffinity as structural indicator of protocoldependent plasticity in amorphous solids Bin Xu, Michael Falk, Sylvain Patinet, Pengfei Guan Structural heterogeneity of amorphous solids is intimately connected to their mechanical behavior. Based on a perturbation analysis of the potential energy landscape, we derive a new structural indicator, termed the atomic nonaffinity, which qualifies the contribution of an individual atom to the total nonaffine modulus. We find that the atomic nonaffinity can efficiently characterize the locations of shear transformation zones (STZ) as well as their protocoldependent response arising from their orientational nature. We quantitatively show that plastic events tend to happen in the STZs whose softest shear directions are close to the loading shear direction. These results provide new insight towards understanding and characterizing the plastic response of amorphous solids. 
Thursday, March 18, 2021 8:48AM  9:00AM Live 
R20.00003: Understanding The Degree of Cluster Expansions Luis BarrosoLuque, Gerbrand Ceder The cluster expansion (CE) method developed to model disorder in alloys has seen active use in computational materials science since it was proposed 30 years ago. Notable extensions to include multilattice systems, and the use of new regression techniques have established the CE as a standard method in the computational study of multicomponent crystals. Recent interest in high entropy alloys (HEA) and cationdisordered rocksalt (DRX) cathode materials has opened a prime setting for continued development of the CE. Studying large multicomponent systems involves exploration of highdimensional spaces. Although the current formulation of the CE is applicable in these highdimensional spaces, issues surrounding specific sampling and regression techniques necessary to obtain manageable and accurate models for treatment of HEA and DRX material systems remain largely unsettled. We reexamine the CE formalism, and explore the relationship of structural relaxations and composition in setting the maximal degree of the CE. Limiting the degree while preserving predictive accuracy is crucial in controlling model complexity and ensuring interpretability needed for successful use of the CE when studying large multicomponent systems. 
Thursday, March 18, 2021 9:00AM  9:12AM Live 
R20.00004: Randomfield Ising model criticality in glassforming liquids Benjamin Guiselin, Ludovic Berthier, Gilles Tarjus The randomfirst order transition (RFOT) theory explains the slowing down of supercooled liquids with an underlying thermodynamic transition to an ideal glass phase below the experimental glass transition T_{g}. At the meanfield level, this transition is exactly realized and RFOT theory also predicts a firstorder transition line ending at a critical point, when the overlap order parameter [1] (quantifying similarity between equilibrium liquid configurations) is linearly coupled to an external field ε. To assess the fate of meanfield results in finite dimensions, we use computer simulations to investigate the extended phase diagram (ε,T) of a 3D model supercooled liquid. Combining umbrella sampling techniques with an extensive finitesize scaling analysis, we demonstrate the existence of a firstorder transition line and of a randomfield Ising model critical point in the thermodynamic limit [2]. This result represents the only piece of the meanfield theory to survive other than as a crossover the introduction of finitedimensional fluctuations. 
Thursday, March 18, 2021 9:12AM  9:24AM Live 
R20.00005: Fieldinduced freezing in the unfrustrated Ising antiferromagnet Adam Iaizzi We study instantaneous quenches from infinite temperature to well below T_{c} in the twodimensional (2D) square lattice Ising antiferromagnet in the presence of a longitudinal external magnetic field. Under singlespinflip Metropolis algorithm Monte Carlo dynamics, this protocol produces a pair of metastable magnetization plateaus that prevent the system from reaching the equilibrium ground state except for some special values of the field. This occurs despite the absence of intrinsic disorder or frustration. We explain the plateaus in terms of local spin configurations that are stable under the dynamics. Although the details of the plateaus depend on the update scheme, the underlying principle governing the breakdown of ergodicity is quite general and provides a broader paradigm for understanding failures of ergodicity in Monte Carlo dynamics. See also: Iaizzi, Phys. Rev. E 102 032112 (2020), doi:10.1103/PhysRevE.102.032112 
Thursday, March 18, 2021 9:24AM  9:36AM Live 
R20.00006: A scaling law describes the spinglass response in theory, experiments and simulations Ilaria Paga, Qiang Zhai, Marco BaityJesi, Enrico Calore, Jose Miguel GilNarvion, Antonio GordilloGuerrero, David Iñiguez, Andrea Maiorano, Enzo Marinari, Victor MartinMayor, Javier MorenoGordo, Antonio MuñozSudupe, Denis Navarro, Raymond Orbach, Giorgio Parisi, Sergio PerezGaviro, Federico RicciTersenghi, Juan Jesús RuizLorenzo, Sebastiano Fabio Schifano, Beatriz Seoane, Alfonso Tarancon, Raffaele Tripiccione, David Yllanes, Andrés Cruz, Luis Antonio Fernández The dynamical arrest found upon cooling glass formers to their glass temperature T_{g} is caused by the unbounded expansion of cooperative regions as T_{g} is approached or as the system is left to age below T_{g}. It is extremely difficult to measure quantities that are accessible both to experiment and simulations, which has led to seemingly irreconcilable approaches. 
Thursday, March 18, 2021 9:36AM  9:48AM Live 
R20.00007: Temperature Chaos does exists in nonequilibrium spinglass dynamics. Javier MorenoGordo, Marco BaityJesi, Enrico Calore, Andrés Cruz, Luis Antonio Fernández, Jose Miguel GilNarvion, Isidoro GonzalezAdalid, Antonio GordilloGuerrero, David Iñiguez, Andrea Maiorano, Enzo Marinari, Victor MartinMayor, Antonio MuñozSudupe, Denis Navarro, Ilaria Paga, Giorgio Parisi, Sergio PerezGaviro, Federico RicciTersenghi, Juan Jesús RuizLorenzo, Sebastiano Fabio Schifano, Beatriz Seoane, Alfonso Tarancon, Raffaele Tripiccione, David Yllanes Spin glasses exhibit a fragile behavior in response to perturbations such as temperature changes. Specifically, arbitrary small changes in the temperature would lead to a complete reorganization of the equilibrium configuration of the spin glass. This equilibrium phenomenon is named Temperature Chaos [1,2]. 
Thursday, March 18, 2021 9:48AM  10:00AM Live 
R20.00008: Analysis of twolevel systems and mechanical loss of amorphous coatings by noncagebreaking and cagebreaking transitions Jun Jiang, Alec Mishkin, Kiran Prasai, Rui Zhang, Riccardo Bassiri, Martin M Fejer, HaiPing Cheng Thermal noise from amorphous mirror coatings is one of the limiting noise sources for the laser interferometer gravitationalwave observatory (LIGO).[CQG 25.11,114041] In order to better understand the origin of the mechanical loss in amorphous coatings, their energy landscapes have been characterized by the correlated parameter distributions of twolevel systems (TLS). By applying the concept of oxygen cage [J. Chem. Phys. 129, 164507 (2008)], the TLSs we find for pure and doped tantala can be separated into two groups named noncagebreaking transitions and cagebreaking transitions. Noncagebreaking transitions only have small structure changes, while cagebreaking transitions involve at least one large atomatom pair distance change between the initial and final atomic structures. The further mechanical loss calculation of ZrO2doped Ta2O5 models establish a connection between the atomic structure changes and mechanical loss, which shows that the noncagebreaking transitions have higher averaged mechanical loss and are responsible for the large mechanical loss peak near 40K, while the cagebreaking transitions are the majority of transitions and mainly contributed to the loss peak near 120K. 
Thursday, March 18, 2021 10:00AM  10:12AM On Demand 
R20.00009: Transverse Collective Modes of Supercooled Liquids Obtained from Stress and Current Correlators Alexander Fullmer, Jacob Eapen A supercooled liquid is a disordered aperiodic system of atoms obtained by rapidly freezing a viscous liquid. One distinguishing characteristic of a supercooled liquid is the tendency of atoms to be trapped by their nearest neighbors engendering a long relaxation time. Several dynamic variables exhibit the extended relaxation process. In this work, we employ atomistic simulations on model glass forming liquids to investigate the shear stress correlations and the attendant relaxation behavior. A range of spatial and temporal scales is probed by analyzing the stress correlations at small, medium and large wavevectors; in the long wavelength limit, the integral of the shear stress correlation (SSC) function provides the shear viscosity. At short wavelengths, the SSC function behaves similar to a normal liquid; from our simulations we draw out the caging effect that results in extended relaxation at longer wavelengths. We also compute the shear viscosity at finite wavelengths through the hydrodynamic relationship with the transverse current correlation (TCC) function. The purpose of this presentation is to provide a description of transverse collective modes in supercooled liquids through the SSC and TCC functions at finite wavelengths. 
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