Bulletin of the American Physical Society
2024 APS March Meeting
Monday–Friday, March 4–8, 2024; Minneapolis & Virtual
Session K58: Electrons, Phonons, Electron-Phonon Scattering, and Phononics VFocus
|
Hide Abstracts |
Sponsoring Units: DCOMP Chair: Shashi Mishra, Binghamton University Room: 205D |
Tuesday, March 5, 2024 3:00PM - 3:36PM |
K58.00001: Abstract Withdrawn Invited Speaker:
|
Tuesday, March 5, 2024 3:36PM - 3:48PM |
K58.00002: Impact of phonons on the phase stability of FCC alloys Chenhui Hu, Lingrui Fan, Xun-Li Wang Phase competition in multi component high-entropy alloys (HEAs) leads to the emergence of exceptional mechanical properties. However, the complex chemistry provides a huge composition space to explore, making it a great challenge to study the mechanisms of competing crystal structures. In this study, we focused on the Co-Ni binary alloy as a simplified model system for these complex alloys. Through inelastic neutron scattering (INS) and differential scanning calorimetry (DSC) measurements, we examine the impact of phonons (vibration) on the phase stability of Co75Ni25. Our first-principles calculations on a model Co-Ni random solid solution at 0K show a good agreement with our experimental phonon density of states data measured by the INS. Our work emphasizes the importance of vibrational entropy on the phase stability, where vibration rather than other contributions dominate the entropy term leading to the stability of the FCC phase in Co75Ni25. |
Tuesday, March 5, 2024 3:48PM - 4:00PM |
K58.00003: Observation of phonon softening in CrCoNi medium entropy alloy Lingrui Fan, Chenhui Hu, Xun-Li Wang Medium entropy alloys (MEAs) are a class of single-phase multicomponent alloys with three elements, known for their distinctive mechanical and physical properties. Specifically, face-centered cubic (FCC) CrCoNi MEA exhibits remarkable tensile strength, uniform elongation, and fracture toughness. However, there is limited experimental understanding of the phonon behavior, which plays a vital role in thermal and elastic properties in MEAs. In this study, we measured the phonon density of states and phonon dispersion curves of CrCoNi MEA using inelastic neutron scattering. We have observed signatures of phonon softening near the Brillouin zone boundary, in comparison with phonon dispersions in FCC Ni and binary CoNi-based systems. We will discuss the influence of chemical disorder on the observed softening mode and its implications for the elastic and thermal properties of MEAs. |
Tuesday, March 5, 2024 4:00PM - 4:12PM |
K58.00004: Strain dependence of phonons in α-uranium Mark A Mathis, Chris A Marianetti The phonons in orthorhombic α-uranium have been well studied due to the charge density wave state, yet a systematic study of the phonons as a function of strain has yet to be accomplished. Here we compute the phonons and anharmonicity in α-uranium using the irreducible derivative method, guaranteeing the highest computational efficiency for a finite displacement method. Various functionals within density functional theory are used to study the change in phonons with respect to the lattice parameters, with particular focus on changes in the soft-modes. Soft phonon modes other than the mode associated with the charge density wave are also found, which have not yet been identified in previous studies. Quartic phonon interactions associated with all soft modes are computed, allowing for the computation of thermal expansion within the Hartree-Fock approximation for phonons. |
Tuesday, March 5, 2024 4:12PM - 4:24PM |
K58.00005: Peltier effect of phonons driven by electromagnetic waves Hiroaki Ishizuka In semiconductors, a steady electric current causes a temperature gradient in a material, which is known as the Peltier effect. The Peltier effect is an example of the thermoelectric effect, which is a consequence of the energy current carried by charged carriers. As the thermoelectric effect is caused by the energy flow of electrons or holes, an analogous phenomenon can occur by a flow of other quasi-particles, such as magnons and phonons. In fact, a spin current analog of the Seebeck effect, another thermoelectric effect, is observed in magnetic insulators, in which case magnons and spinons carry the spin angular momentum. On the other hand, as accelerating magnons and phonons by the electromagnetic field is difficult, an analog of the Peltier effect, that is, externally controlling the temperature gradient by inducing the flux of quasiparticles, remains a challenge. |
Tuesday, March 5, 2024 4:24PM - 4:36PM |
K58.00006: Photoactivated Ligand Exchange Dynamics in Tungsten-Complexes: A TDESMD Approach dmitri kilin, KAMRUN NAHAR KEYA, Yulun Han, Wenfang Sun, Wenjie Xia, Bakhtiyor Rasulev, Svetlana Kilina Transition-metal complexes (TMCs) play a pivotal role in areas such as optoelectronics, solar energy conversion, and biomedical applications. In this study, we delve deep into the dynamics of ligand exchange reactions in six distinct W(CO)4(bpy) complexes using time-dependent excited-state molecular dynamics (TDESMD)1,2 based on Rabi oscillations between ground and excited states under optical irradiation. Our objective is to explore the mechanism of how the photo-induced charge transfer dynamics facilitates the mechanistic pathway in which a mix of W(CO)6 and bipyridine (bpy) transforms into a W(CO)4(bpy) complex. Preliminary findings suggest that the photoreactions are facilitated by excited states corresponding more closely to ligand-to-metal charge transfer (LMCT) character. It is this photoactivation, particularly of the LMCT type, that weakens the W-C bonds, thereby facilitating the subsequent dissociation of CO ligands. Consequently, this gives rise to the reactive W(CO)5 radical, which then establishes a coordination bond with the nitrogen of the bpy ligand. At the next stage, second CO ligand desorbs allowing for formation of two stable coordination bonds between tungsten and bpy. Several approaches have been committed to explore the possibility of the subsequent formation of W(CO)2(bpy)2. And W(bpy)3 complexes. Our study enables the exploration of the pathways of photoactivated reaction dynamics and assessment of the intermediates formed during the reaction and the transition states along this path. Such insights are instrumental in interpreting synthetic endeavors, aiming for an efficient exploration of near-infrared (NIR) emitters composed of earth-abundant metals and a variety of organic ligands. |
Tuesday, March 5, 2024 4:36PM - 4:48PM |
K58.00007: Machine Learning-Driven Predictions of Crystal Symmetry Groups Using Chemical Compositions in Binary and Ternary Materials Mohammed Alghadeer, Yousef A Alghofaili, Abdulmohsen A Alsaui, Saad M Alqahtani, Fahhad H Alharbi Emphasizing the intersectionality of materials science and physics, this work investigates the profound problem of predicting crystal structures solely based on chemical compositions, a daunting task in condensed matter physics. Leveraging minimalistic, yet impactful, ionic and compositional features such as stoichiometry, ionic radii, and oxidation states, we engineered highly accurate Machine Learning (ML) classifiers capable of predicting crystallographic symmetry groups, even with the complex, multi-label, multi-class nature of the problem [1, 2]. Focusing on ternary (Al Bm Cn) and binary (Al Bm) materials, the developed ML models exhibit high accuracy across various symmetry groups, including crystal systems, point groups, Bravais lattices and space groups, with weighted balanced accuracies surpassing 95% even in the context of size-imbalanced data [3, 4]. This underlines that intrinsic physics is well-represented, further substantiated by illustrating the accuracy of the models aligning closely with the available data size. This pioneering approach not only provides a potential solution to an age-old problem but propels forward the expedition in discovering and developing new materials by embedding predictive analytics at its core, combining physics-informed features with data-driven methodologies. |
Tuesday, March 5, 2024 4:48PM - 5:00PM |
K58.00008: Density functional latent space representations of dynamical densities and potentials Susan R Atlas The combinatorically-large phase space of possible interactions among atomic elements represents both a challenge and an opportunity for machine learning the structures and compositions of novel and useful biomolecules and materials. There is growing interest in combining physics-based models with purely data-driven approaches, in order to optimize the fidelity and efficiency of interaction potentials for atomistic molecular dynamics simulations. The ensemble-charge transfer embedded atom method (ECT-EAM)1 utilizes energy functionals and atomic density latent variables to flexibly represent complex and dynamically-evolving quantum mechanical interactions among atoms, including bond formation and breaking. We describe the principled construction of these latent variables from density functional theory, and show how it effects a rigorous coupling between the electronic and atomistic length scales. We also discuss how a latent variable neural network representation of the electron density can provide surprising insight into the balance between ionic and covalent bonding as a function of molecular geometry. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700