Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session A48: Electronic Structure MethodsRecordings Available

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Sponsoring Units: DCOMP Chair: Eric Switzer, Univerity of Central Florida Room: McCormick Place W471A 
Monday, March 14, 2022 8:00AM  8:12AM 
A48.00001: MOPAC and semiempirical models: past and future Jonathan E Moussa Semiempirical electronic structure originated as a stopgap from a time when firstprinciples electronic structure calculations 
Monday, March 14, 2022 8:12AM  8:24AM 
A48.00002: Benchmark calculations of the energy spectrum and oscillator strengths of the beryllium atom Sergiy Bubin We have performed a comprehensive set of benchmark variational calculations for the ground and 19 lowest bound excited singlet S and P states of the beryllium atom. The nonrelativistic wave functions of the states that represent the motion of the nucleus and the four electrons around the center of mass of the atom have been expanded in terms of up to 17000 allparticle explicitly correlated Gaussians that were extensively optimized for each state independently. The leading relativistic and QED corrections to the energy levels have been computed in the framework of the perturbation theory and they explicitly include the nuclear recoil effects. This has allowed us to reach subwavenumber accuracy for all 20 states. Using the obtained energy levels and the corresponding wave functions, we have computed the transition frequencies, transition dipole moments, and oscillator strengths. A comparison with the experimental data aggregated in NIST ASD database shows very good agreement, except for the 7th excited singlet P state, for which the available experimental data is likely to contain an error. 
Monday, March 14, 2022 8:24AM  8:36AM 
A48.00003: In Situ Pseudopotentials: Calculating pseudopotentials using allelectron theory for solid Chin Shen Ong, Kristofer Björnson, Vladislav Borisov, John M Wills, Mebarek Alouani, Oscar Grånäs, Patrik Thunström, Olle Eriksson We present a general method of constructing in situ pseodopotentials from firstprinciples, allelectron, and fullpotential electronic structure calculations of a solid. The method is applied to bcc Na, at lowtemperature equilibrium volume. The essential steps of the method involve (i) calculating an allelectron KohnSham eigenstate, (ii) replacing the oscillating part of the wave function (inside the muffintin spheres) of this state with a smooth function, (iii) representing the smooth wave function in a Fourier series, and (iv) inverting the Kohn−Sham equation, to extract the pseudopotential that produces the state generated in steps (i)−(iii). It is shown that an in situ pseudopotential can reproduce an allelectron fullpotential eigenvalue up to the sixth significant digit. A comparison of the allelectron theory, in situ pseudopotential theory, and the standard nonlocal pseudopotential theory demonstrates good agreement, e.g., in the energy dispersion of the 3s band state. 
Monday, March 14, 2022 8:36AM  8:48AM 
A48.00004: Obtaining a faster convergence to the thermodynamic limit for metals using structure factor twist averaging Tina N Mihm, Tobias Schäfer, Sai Kumar Ramadugu, Laura Weiler, Andreas Grueneis, James J Shepherd As metals play a large role in material design applications such as catalysis and surface chemistry, there is a crucial need for efficient and accurate wavefunctionbased calculations. However, there is still a large computational cost due to larger finite size errors associated with methods such as coupled cluster that currently prohibit wide application to metals. While methods such as twist averaging can be used to reduce the finite size errors through use of offsets to kpoint grids called twist angles, these methods often add an additional computational time cost due to requiring multiple calculations. Here, I will show how we use our new structure factor twist averaging method to address this issue through finding a single twist angle that represents the twist averaged system. With this special twist angle, we can achieve the desired reduction in finite size errors while providing a cost reduction up to two orders of magnitudes. I will demonstrate the effectiveness of our method through showing several applications to various metallic systems as well as a range of insulators and semiconductors. 
Monday, March 14, 2022 8:48AM  9:00AM 
A48.00005: Clifford boundary conditions for the study of periodic Coulomb systems Jan A Berger, Stefano Evangelisti, Gian Luigi Bendazzoli, Véronique Brumas, Miguel Escobar Azor, Estefania Alves, Nicolas Tavernier We propose an original and general approach for the numerical study of periodic Coulomb systems. In our formalism we change the topology of a supercell into the topology of a torus. However, in order to maintain the regular structure of the system, and, in particular, the angles, we use a Clifford torus. A Clifford torus is a real, flat and closed ddimensional Euclidean space embedded in a complex ddimensional Euclidean space. Moreover, we renormalize the distance between two points on the Clifford torus as the distance between these points in the embedding space of the torus and use this renormalized distance in the Coulomb potential. We have, so far, successfully applied this strategy to the calculation of Madelung constants and Wigner crystals. We also propose a new position operator that is compatible with periodic boundary conditions and satisfies all appropriate physical constraints. The position operator and the renormalized distance are consistent with each other. 
Monday, March 14, 2022 9:00AM  9:12AM 
A48.00006: Helical waves for selfconsistent first principles calculations of chiral onedimensional nanomaterials Olivia E Liebman, Shivang Agarwal, Amartya S Banerjee Chiral nanomaterials  particularly, onedimensional (1D) structures – offer unparalleled opportunities for impacting the design of novel quantum, photonic and electromagnetic devices due to their unique (and sometimes anomalous) transport, optical, electric, and magnetic properties. We describe our efforts in formulating and implementing a selfconsistent first principles simulations framework to enable the discovery and characterization of novel forms of such materials. Since conventional first principles methods, based on planewaves e.g., are unable to suitably accommodate the helical potentials commonly associated with these structures, our methodology consists of expressing the equations of KohnSham Density Functional Theory using Helical Bloch states and discretizing the resulting equations using specialized Laplacian eigenfunctions called Helical waves. Embedded within the equations of KohnSham theory is the problem of electrostatics, which we tackle using a mixed spectralfinite difference formulation in our framework. We demonstrate our method using numerous examples of chiral 1D nanomaterials with intrinsic or applied twist, and describe the utility of our technique to study topological phases and/or correlated electronic states that may emerge in such systems. 
Monday, March 14, 2022 9:12AM  9:24AM 
A48.00007: A multipole approach for dielectric screening in metallic systems Dario A Leon Valido, Claudia Cardoso, Daniele Varsano, Elisa Molinari, Andrea Ferretti The plasmon pole (PPA) model is a popular approximation adopted for treating the frequency dependence in GW. This method has been successfully applied to a large variety of systems ranging from insulators and semiconductors, the homogeneous electron gas and simple metals like Al and Na. In contrast, metals with small plasmon energies, such as Ni, Cu and Co, are particularly challenging for simple models like in PPA, since they present strong screening effects resulting in multiple plasmonic excitations. In these cases a more accurate but computationally costly full frequency (FF) approach is usually preferred. 
Monday, March 14, 2022 9:24AM  9:36AM 
A48.00008: Bonddependent slaveparticle cluster theory Zheting Jin, Sohrab IsmailBeigi General and exact solutions of large, stronglycorrelated electron problems, exemplified by the Hubbard model on a lattice, are challenging. A wide variety of approaches exist in the field, and recent occupationnumber based slaveparticle methods [14] represent a computationally efficient approach. Here, one decoupling the electronic spin and charge degrees of freedoms to end up with a noninteracting fermion problem on the lattice and an interacting auxiliary slave problem on the lattice. One must then truncate or simplify the slave problem to render it tractable. 
Monday, March 14, 2022 9:36AM  9:48AM 
A48.00009: Reduced densitymatrix from the GW approximation Fabien Bruneval, Mauricio RodriguezMayorga, Marc Torrent, Patrick Rinke, Marc Dvorak The GW approximation is well known for the calculation of highquality ionization potentials and electron affinities in solids and molecules. However, the Green's function contains much more information than the mere quasiparticle energies. In particular, the instantaneous Green's function G(r, r', tt'=0^{}) is nothing else but the celebrated onebody reduced densitymatrix. The densitymatrix gives a direct access to many physical observables: electronic density, kinetic, Hartree and exchange energies, etc. 
Monday, March 14, 2022 9:48AM  10:00AM 
A48.00010: Reducedgradient analysis of van der Waals complexes Trevor Jenkins, Kristian Berland, Timo Thonhauser Different methods to describe dispersion interactions within DFT have been developed, which are essential to describing binding in van der Waals complexes. However, key properties such as binding energies, lattice constants, and binding distances also depend on the exchange description. Here, we present an analysis of the reducedgradient values that determine the semilocal exchange for different classes of van der Waals complexes. We analyze molecular dimers, layered structures, surface adsorption, and molecular crystals. We find that reducedgradient values of less than ~1 contribute attractively to the exchange binding, while higher values are repulsive. The attractive contributions can be attributed to lowdensity regions between the constituents with disklike isosurfaces. We identify a mechanism wherein the merging of isosurfaces switches the gradientcorrection to exchange from attractive to repulsive. This finding allows us to develop a generalized picture of the bond formation in weakly bonded materials in terms of the topology of their reducedgradient isosurfaces. This picture also uncovers desirable features of the exchange enhancement factor and can be used to understand why methods perform differently for different classes of van der Waals systems. 
Monday, March 14, 2022 10:00AM  10:12AM 
A48.00011: Defect levels in doped silicon using Koopmans spectral functionals Riccardo De Gennaro, Nicola Marzari, Nicola Colonna, Edward Linscott Substitutional defects in insulating crystalline materials lead to the formation of impurity levels within the forbidden gap that play an essential role in determining the properties of electronic devices. The need for large supercells has often limited the simulation of these systems to standard densityfunctional theory calculations precluding access to spectral properties. In this work we address this class of problems using Koopmanscompliant functionals, that are a novel orbitaldensitydependent approach that describes accurately charged excitations and the electron addition/removal processes. Given the success in the description of the band structure of semiconductors and insulators  with results comparable to stateoftheart manybody perturbation theory methods  here we use Koopmans functionals to predict the energy levels of defects in doped silicon. 
Monday, March 14, 2022 10:12AM  10:24AM 
A48.00012: Accurate. Calculated, Electronic and Transport Properties of Zinc Blende Indium Arsenide (zbInAs) Yuriy Malozovsky, Yacouba I Diakite, Cheick Oumar Bamba, Lashounda Franklin, Diola Bagayoko We report theoretical results on electronic and transport properties of zinc blende indium arsenide (zbInAs). In these abinitio, selfconsistent calculations, we used a local density approximation (LDA) potential and the linear combination of atomic orbital (LCAO) formalism. With performed a generalized minimization of the energy, with the Bagayoko, Zhao, and Williams (BZW) method, to reach the ground state of the materials without using overcomplete basis sets. Consequently, our results have the full, physical content of density functional theory (DFT) and agree with available, corresponding experimental ones. With an experimental room temperature lattice constant of 6.0583Ȧ, we obtained a direct band gap of 0.360 eV, in excellent agreement with room temperature measurements. This finding is in stark contrast with results from 27 previous abinitio DFT calculations that reported negative numbers or zero for the band gap of zbInAs. We reproduced the correct locations of the major peaks in the total density of valence states. We present additional results on the partial densities of states and the electron and hole effective masses. The latter two also agree with corresponding, experimental values. 
Monday, March 14, 2022 10:24AM  10:36AM Withdrawn 
A48.00013: Tailoring Electronic Properties of Bi_{2}Te_{3} with Parametrized TightBinding Corrections to Density Functional Theory Wannier Matrix Elements Shima Sharifi Najafabadi, Stephen Fahy, Ivana Savic For decades, Bi_{2}Te_{3} has been the best candidate for thermoelectric applications near room temperature. Density functional theory (DFT) fails to reproduce its known experimental features. The maximally localized Wannier approach [1] accurately reproduces the DFT bands, whereas traditional parameterized tightbinding models, while incorporating experimental knowledge, are limited to a small number of parameters and cannot describe all aspects of the bands. To correct these deficiencies, we combine the strengths of each approach, modifying the DFT Wannier Hamiltonian with small corrections, that are transferred to the matrix elements in a consistent way from an intuitively simple parameterized tightbinding form. In this hybrid approach, the DFT singleparticle Hamiltonian is the baseline and corrections are added to its matrix elements to finetune the bands near the Fermi energy. Our method can be generalized to other systems, including Bi_{2}Te_{3}based alloys, estimating carrier effective masses and alloy scattering to identify the optimal alloy composition for thermoelectric performance. 
Monday, March 14, 2022 10:36AM  10:48AM 
A48.00014: Ab initio Approaches to High Entropy Alloys  A comparison of CPA, SQS, and Supercell methods Mariia Karabin, Markus Eisenbach, Yang Wang, George M Stocks, Hanna Terletska, Wasim R Mondal, KaMing Tam, Vladimir Dobrosavljevic, Liviu Chioncel, WaiGa D Ho, Xianglin Liu High entropy alloys (HEA) are a great approach to multicomponent alloy design with disorder being stabilized by the high configurational entropy. The most common for these alloys are simple structures (e.g. bodycentered cubic) with extremely high chemical disorder. Typically, HEA are composed of four or more principal components to achieve high entropy of mixing, which results in alloys with highly tunable properties. 
Monday, March 14, 2022 10:48AM  11:00AM 
A48.00015: An investigation of high entropy alloy electrical conductivity using firstprinciples calculations Vishnu Raghuraman, Yang Wang, Michael Widom The Kubo–Greenwood equation, in combination with the firstprinciples Korringa–Kohn–Rostoker coherent potential approximation (KKRCPA) can be used to calculate the DC residual resistivity of random alloys at T = 0 K. We implemented this method in a multiple scattering theory based ab initio package, MuST, and applied it to the ab initio study of the residual resistivity of the high entropy alloy Al_{x}CoCrFeNi as a function of x. The calculated resistivities are compared with experimental data. We also predict the residual resistivity of refractory high entropy alloy MoNbTaV_{x}W. The calculated resistivity trends are also explained using theoretical arguments. We also discuss the inclusion of chemical short range order effects in the conductivity calculations by combining the KuboGreenwood equation with the Cluster Averaged Coherent Potential Approximation. 
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