Bulletin of the American Physical Society
89th Annual Meeting of the Southeastern Section of the APS
Volume 67, Number 18
Thursday–Saturday, November 3–5, 2022; University of Mississippi, University, MS
Session A01: Exotic Physical Properties, Measured and Modeled |
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Chair: Ruiqi Zhang, Tulane University Room: University of Mississippi Ballroom A |
Thursday, November 3, 2022 8:30AM - 9:00AM |
A01.00001: Topological Materials for Thermoelectric Applications Invited Speaker: Cheng-Chien Chen Topological insulators and topological semimetals have potential important application in thermoelectric technology. Here, I will present density functional theory (DFT) simulations of transport properties in lanthanum monopnictides LaP and LaAs, and show that strain engineering can substantially improve their figure of merit ZT values for high-temperature thermoelectric applications. I will also discuss families of type-II Weyl semimetals that exhibit large anisotropic in-plane Seebeck coefficients. Our DFT calculations predict that electron doping these materials to ~0.2 eV higher could lead to the largest ever reported transverse thermoelectric response. Finally, I will discuss machine learning prediction of lattice thermal conductivity. Several compounds are predicted to exhibit ultra-low lattice thermal conductivity (< 1W/mK), some of which are also promising low-temperature thermoelectric materials. |
Thursday, November 3, 2022 9:00AM - 9:30AM |
A01.00002: Mechanical and thermal properties of carbon linear chains encapsulated by carbon nanotubes Invited Speaker: Paulo T Araujo Linear carbon chains (LCCs) are one-dimensional materials with unique properties and restricted selection rules for phonon-phonon and electron-phonon interactions. When encapsulated by carbon nanotubes (CNTs), these LCCs find a suitable environment to keep themselves stable. In this seminar, the Raman spectroscopic signature C-band around 1850 cm$^{−1}$ from LCCs encapsulated by CNTs is monitored against pressure (P) and temperature (T) and its behavior reveals: (1) unique mechanical properties showing that the LCCs' Young's modulus, Grüneisen parameter and strain follow universal P$^{−1}$ and P$^{2}$ laws, respectively; and (2) unique thermal properties showing that the LCCs' thermal properties are well described within the Debye formalism even at room temperatures leading to unique universal relations for their internal energy, heat capacity, coefficient of thermal expansion and thermal strain in terms of the number of carbons atoms and T. |
Thursday, November 3, 2022 9:30AM - 9:42AM |
A01.00003: ElphonPy: A Simple Interface Expediting Electron-Phonon Calculations and Analysis using EPW Code Adam D. Smith, Cheng-Chien Chen Electron-phonon interactions play an important role in a variety of physical properties, including transport, thermodynamics, and BCS superconductivity. Many density functional theory (DFT) calculations need to be performed in order to study these interactions and require careful tuning of calculation parameters to replicate physical experiments. A key requirement for high-throughput computational material science is the development of tools capable of performing input file setup, setting up calculation routines, post-calculation analysis, and data organization. The Electron-phonon Python (ElphonPy) library is a toolkit designed to facilitate the use of the Electron Phonon Wannier (EPW) software in conjunction with Quantum Espresso (QE) with Python. ElphonPy aims to aggregate tools for high-throughput computation into a singular python library for researchers to study many materials of interest quickly and easily. In this presentation we will demonstrate several features of ElphonPy through examples on well known BCS superconductors, NbTi and MgB2. |
Thursday, November 3, 2022 9:42AM - 9:54AM |
A01.00004: First-Principles Modeling of Structural and Mechanical Properties of High-Entropy Borides Luke C Moore, Cheng-Chien Chen High-Entropy Materials are of substantial interest due to their desirable properties, which include stability at high temperatures, oxidation resistance, high hardness, to name a few. However, an accurate prediction of the properties of these materials is particularly challenging due to the number of combinatoric possibilities – both in structure and composition. To overcome the challenge, we consider two distinct structural generation techniques, Special Quasi-Random Structures (SQS) and Automated FLOW Partial Occupation (AFLOW-POCC), as well as a quantity known as the Entropy Forming Ability to predict the synthesizability of high-entropy materials. Since these materials are stabilized by entropy effect at high temperature, harmonic phonon approximations can fail. We thereby also explore ab initio molecular dynamics (AIMD) calculations to predict the dynamic properties and PVT curves. We believe that each of these techniques utilized in conjunction enables powerful predictive power of high-entropy material properties for laboratory verification. |
Thursday, November 3, 2022 9:54AM - 10:06AM |
A01.00005: Not All Uniform B-Fields Are The Same! Benjamin K Luna, Murray S Daw Set up a uniform B-field in the z-direction and place a rectangular-plate capacitor with its plates parallel to the B-field. Quasistatically turn off the B-field – what happens? We show that this seemingly simple and innocuous question which appears in a famous undergraduate E&M textbook hides behind it several things about the nature of E&M which must overturn our attitude regarding the magnetic vector potential. These insights are normally obscured by the standard formulation of electrodynamics in terms of the E and B fields, and this standard formulation hinders students and professional physicists alike from a fully physical understanding of electromagnetic induction. We resolve this problem by introducing the vector potential and showing the physical nature which it captures and that the B-field leaves out. Additionally, the physical significance of gauge transformations will be discussed. This will demonstrate by a purely classical argument that the vector potential is a real specification of the B-field, and that not all uniform B-fields are the same! This theoretical insight will have applications to the Hall effect in condensed matter physics. |
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