Bulletin of the American Physical Society
2015 Annual Meeting of the APS Mid-Atlantic Section
Volume 60, Number 14
Friday–Sunday, October 23–25, 2015; Morgantown, West Virginia
Session A5: Materials Modeling |
Hide Abstracts |
Chair: James Lewis, West Virginia University Room: Waterfront Hotel Wharf AB |
Saturday, October 24, 2015 10:30AM - 10:42AM |
A5.00001: Electron correlations in solids from the Dynamical Mean Field perspective and the origin of the anomalous state of matter in iron pnictides and chalchogenides Invited Speaker: Kristjan Haule Materials with strong electronic correlations have long resisted abinitio modeling due to their complexity arising from non-perturbative strength of the interaction. The Dynamical Mean Field Theory in combination with the Density Functional Theory has recently changed that, and enabled detailed modeling of the electronic structure of many complex materials, such as the heavy fermions, transition metal oxides, iron superconductors. I will give basic foundation of this theory from the functional point of view, and an overview on the recent advances in this field. As an example, I will discuss the iron superconductors and their anomalous properties, which have their origin in strong Hund's coupling and give rise to physics of Hund's metals.The Dynamical Mean Field Theory simulations not only uncovered the origin of the anomalous properties, but also successfully explained the key properties of these material: such as the mass renormalizations and anisotropy of quasiparticles, the crossover into an incoherent regime above a low temperature scale, and the magnetic excitations in energy and momentum space, the spin dynamics and superconducting pairing symmetry. A novel orbital anti-phase superconducting pairing was discovered, which explains the measured gaps on Fermi surfaces. [Preview Abstract] |
Saturday, October 24, 2015 10:42AM - 10:54AM |
A5.00002: Universality Classes of Weakly Anisotropic 2D Heisenberg Ferromagnets Donald Priour Per the Mermin-Wagner theorem, two dimensional isotropic Heisenberg ferromagnets (i.e. as in a delta doped magnetic semiconductor) are devoid of long range ferromagnetic order at finite temperatures. Nevertheless, even a small degree of anisotropy very effectively stabilizes finite temperature ferromagnetism. The ferromagnetic phase may be divided into two regions, 2D ferromagnets in which the anisotropic term favors orientation of the magnetic moment parallel to the plane, and systems in which the easy axis is perpendicular to the plane. Using large scale Monte Carlo calculations (Wolff cluster updates combat critical slowing down near $T_{c}$) to calculate critical exponents such as $\nu$ and $\mu$ (associated with the correlation length $\xi$ and the magnetization, respectively), we determine the universality class of the magnetic phases in regions where planar moments are favored and those in which perpendicularly oriented moments are preferred. Based on the results, we determine if the isotropic limit is a boundary between two distinct universality classes, if critical exponents vary continuously with the anisotropy parameter, or if planar and vertical easy axis ferromagnetic phases are of the same universality class despite being qualitatively distinct in other ways. [Preview Abstract] |
Saturday, October 24, 2015 10:54AM - 11:06AM |
A5.00003: The Age of Exploration: Materials Discovery in the Virtual World Karin Rabe New materials can solve many (though not all) of the world's problems though faster, smaller-scale and cheaper processing and storage of information and energy. Improving and optimizing the materials we already use for these purposes can only take us so far -- what about something really new? How would we know where to look? Information about the structures and properties of experimentally known materials, as organized into a crystallographic database, provides the initial data for a rough map of the space of possible materials. Using the theory of quantum mechanics to perform first-principles computer simulations of the properties of known and as-yet hypothetical materials from first principles, using only their chemical composition as input, we can augment the database with the results of computer experiments to develop the map. By constructing materials models from first-principles information, we can identify the regions of the map that are the most rewarding for closer study at each stage. As the map develops, we can target relatively little-studied families of materials to identify promising candidate materials with desired properties and provide guidance to experimenters in the real world, allowing them to focus their efforts in the most productive directions; this is the underlying principle of the Materials Genome Initiative of 2011.~ In this talk, I will describe what functional materials are and how they work, with illustrative results including ferroelectrics, antiferroelectrics, multiferroics, and field-controlled metal insulator systems, both in bulk form and in artificial heterostructures. The challenges and promise of theoretical materials design and theoretical-experimental integration will be discussed. [Preview Abstract] |
Saturday, October 24, 2015 11:06AM - 11:18AM |
A5.00004: TBD AvendaƱo-Franco |
Saturday, October 24, 2015 11:18AM - 11:30AM |
A5.00005: Relativistic single-site Green's function for full potential scattering Xianglin Liu, Yang Wang, Markus Eisenbach, G.Malcolm Stocks The Green's function of an electron scattered by a single potential is essential for a multiple-scattering theory (MST) based electronic structure calculation. Robust solver for this single site Green's function has been developed for non-relativistic system, as well as for spherical potential relativistic system, but works on a relativistic full potential (FP) solver are still unsatisfactory. Here a new method to obtain this relativistic-FP Green's function in analogy with the non-relativistic MST has been implemented using the so called phase integral technique. Compared to the previous relativistic-FP method, no matching on the boundary is needed and the coupling of partial waves is not limited to $\Delta l=0$ in this method. As an example, the density of states (DOS) of copper has been calculated using both integral of the Green's function and the Krein theorem and the agreement is shown. This work will be the basis for developing a MST based relativistic ab initio electronic structure calculation method. [Preview Abstract] |
Saturday, October 24, 2015 11:30AM - 11:42AM |
A5.00006: The effects of Li concentration on the structure and mechanics in the Li-Mg binary system Olivia Pavlic, Irais Valencia-Jaime, Aldo Romero Magnesium (Mg) is a low density and naturally abundant material that has received much attention due to structural, mechanical, electrical, and thermal properties. Unfortunately, due to its hexagonal close packed (hcp) structure Mg materials exhibit low ductility and are difficult to work with at room temperature. One way to make Mg suitable for industrial applications is to change its structure by alloying. Lithium (Li) is a good candidate to alloy with Mg because of its more workable body centered cubic (bcc) structure and low density, making LiMg compounds regarded as ultralight materials. We study the Li-Mg binary compounds over varying percents of Li from $0-100\%$ using the minima hopping method for structural search. On our convex hull we find four structures, Li1Mg2 space group I4/mmm, Li1Mg1 space group Pm-3m, Li7Mg2 space group Ibam, and Li9Mg1 space group C12/m1. We note that the Li1Mg2, Li2Mg7, and Li9Mg1 structures are previously unreported. A mechanical and structural characterization is performed over these and six other structures. We present elastic constants, mechanical properties, and structures which outline the effect of the added Li. [Preview Abstract] |
Saturday, October 24, 2015 11:42AM - 11:54AM |
A5.00007: Fermi-orbitals for improved electronic structure calculations on biophysically relevant Molecules Der-you Kao, Mark R. Pederson, James D. Lee An improved density-functional formalism[1,2] proceeds by adopting the Perdew-Zunger expression for a self-interaction-corrected (SIC) density-functional energy but evaluate the total energy based on Fermi Orbitals (FOs). Each localized electron is represented by an FO, determined from the occupied Kohn-Sham orbitals and a semi-classical FO descriptor. The SIC energy is then minimized through the gradients of the energy with respect to these descriptors. Besides providing a review of the calculation of optimization, work here identifies the need for an algorithm which thoroughly searches over initial configurations. The strategy for sampling and prioritizing initial configurations is described. Applications to biophysically relevant spin-polarized molecules, such as Oand molecules containing transition-metal centersare presented. The FO descriptors and FOs for semi-classical and quantum-mechanical understanding of bondingis discussed. Cohesive energies are improved andthe eigenvalues are shifted downward relative to the standard DFT results.Spin-dependent vibrational spectra, as a possible means for spectroscopic determination of the transition-metal moment, are also presented. [1]Pederson et al, JCP 140, 121103(2014). [2]Baruah {\&} Pederson, AAMOPS 64, 153-180(2015). [Preview Abstract] |
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