Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session Q01: Density Functional Theory and Beyond VFocus Recordings Available

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Sponsoring Units: DCP Chair: Eli Kraisler, Hebrew University of Jerusalem Room: McCormick Place W175A 
Wednesday, March 16, 2022 3:00PM  3:36PM 
Q01.00001: Longrange correlations in density functional theory Invited Speaker: Tim Gould Accurate and lowcost reproduction of electron correlations remains one of the most difficult problems in chemical physics. Enormous progress has been made in dealing with shortrange correlations. But longrange correlations remain challenging, despite contributing to a range of important quantum chemical problems including dispersion forces [12], strong correlations [34] and charge transfer excitations [5]. This talk will discuss the origins of key types of longrange correlations in density functional theory, and consider physical, chemical and mathematical perspectives on the problem. It will discuss some lowcost solutions to difficult problems in the field, introduced by the author and others, and will highlight some of the challenges that lie ahead. It will stress the importance of the universal functional in devising new approximations, and how ensembles and the fluctuationdissipation theorem help, even in “mundane” cases. [6] 
Wednesday, March 16, 2022 3:36PM  3:48PM 
Q01.00002: Numerical Estimates of TemperatureDependent Bounds on the ExchangeCorrelation Free Energy Aurora PribramJones, Brittany P Harding, Zachary N Mauri In density functional theory, the LiebOxford bound has been used to constrain popular approximations of the exchangecorrealation density functional. Preliminary evidence from thermal density functional theory supports the existence of a similar, temperaturedependent bound. A wellknown parameterization of the exchangecorrelation free energy of the uniform electron gas is used to generate adiabatic connection curves and generate estimates of these bounds in various temperature and density regimes. Connections to known limiting behaviors of the exchangecorrelation will be discussed. 
Wednesday, March 16, 2022 3:48PM  4:00PM 
Q01.00003: Kinetic peaks and step in the KS potential for molecular dissociation Sara Giarrusso Sharp features, such as peaks and steps, are known to arise in the KS potential to describe molecular dissociation [1] and can be traced back to welldefined components of the total KS potential, the socalled (correlation) kinetic and response ones. 
Wednesday, March 16, 2022 4:00PM  4:12PM 
Q01.00004: Strong correlation in DFT at finite temperatures: the case of the Hubbard dimer. Juri Grossi, Aurora PribramJones Density Functional Theory and its finitetemperature extension are a workhorse for electronic structure calculations and the study of warm dense matter properties. In its KohnSham formulation, much effort is devoted to approximate exchangecorrelation effects, often neglecting completely temperature effects. 
Wednesday, March 16, 2022 4:12PM  4:24PM 
Q01.00005: Towards Probabilistic Analysis of Entropy Stabilized Oxides using Density Functional Theory Lily J Joyce, Kristen E Johnson, Christina M Rost, Kendra L LetchworthWeaver Entropy Stabilized Oxides (ESOs) [1] are novel materials with many potential applications in modern technology, including in thermoelectric devices and battery cathodes. These materials are enthalpically unfavorable, but entropically favorable due to high configurational disorder, making them a challenge to analyze using enthalpy based methods such as Density Functional Theory (DFT). To achieve this goal, we have created Pythonbased software which randomizes the placement of metal cations in a rocksalt lattice, creating an ensemble of microstates for the local environment of an ESO. DFT is used to determine the enthalpy of formation from the single phase metal oxides for each microstate within the ensemble. We then create a statisticalmechanical model based on the DFT computed enthalpies of the microstates by computing the expectation values of relevant energetic, structural, and electronic properties over the entire ensemble of structures. The efficacy of our approach may be tested by direct comparison to experimental characterization such as Xray diffraction (XRD) and Xray absorption spectroscopy (XAS). 
Wednesday, March 16, 2022 4:24PM  4:36PM 
Q01.00006: Analyzing exchangecorrelation temperature dependence via the generalized thermal adiabatic connection Zachary N Mauri, Aurora PribramJones The warmdense matter regime is an intermediate phase of matter that blurs the boundary between solids and plasmas, with characteristics of both presenting unique theoretical challenges. We combine the formalism of the adiabatic connection, which allows us to smoothly navigate from the noninteracting KohnSham system to the real, fully interacting system of interest, with additional entropic contributions to approximate the finitetemperature exchangecorrelation free energy. I will present equations describing these entropic contributions using the generalized thermal adiabatic connection. Evaluation of the approximation will be preformed using the halffilled Hubbard dimer at large onsite interaction strength to test the accuracy of the GTAC approaches for the strongly correlated regime. 
Wednesday, March 16, 2022 4:36PM  4:48PM 
Q01.00007: Generating the TemperatureDependence of PBE John Kozlowski, Kieron Burke FiniteTemperature Density Functional Theory (FTDFT) has been instrumental to the study of warm dense matter in the past few decades. However, even the best of our modern calculations are imperfect, and typically make use of ground state functionals that ignore the temperaturedependence of the exchangecorrelation energy. The effects of this limitation are unknown, but may play a significant role in our understanding of warm dense matter. To correct this, we derive the temperaturedependence of PBE through a scheme of KohnSham calculations [1] that yield accurate exchangecorrelation holes at finite temperatures. 
Wednesday, March 16, 2022 4:48PM  5:00PM 
Q01.00008: Building a beyondDFT database of spectral functions for correlated materials Subhasish Mandal, Kristjan Haule, Karin M Rabe, David Vanderbilt Generating databases of the electronic structure of materials is a key to datasciencedriven materials discovery. Many existing materials databases, which were constructed in the spirit of the Materials Genome Initiative, rely almost exclusively upon DFT engines and often make incorrect predictions for many correlated materials. Because qualitative predictions of excitedstate properties usually require beyondDFT methods, various advance methods such as metaGGAs, hybrid functionals, GW, and dynamical meanfield theory (DMFT) have been developed to describe the electronic structure of correlated materials. However, the expected accuracy of these methods when applied to various classes of materials remains unclear. It is thus of pressing interest to compare their accuracy for different types of materials, and at the same time, to build a broad publiclyavailable database of the results of beyondDFT calculations. In this talk, I will discuss some of the challenges involved in generating such a beyondDFT database using highthroughput computations, and show how we have overcome these challenges in our systematic study of these methods on various training sets of moderately and strongly correlated materials. 
Wednesday, March 16, 2022 5:00PM  5:12PM 
Q01.00009: Direct orbital optimization methods for variational density functional calculations of excited electronic states Gianluca Levi Excited states can be calculated as stationary states of the energy expressed as a density functional. This variational approach provides atomic forces, can describe doubly excited states and, thanks to statespecific orbital relaxation, gives better approximations of chargetransfer, Rydberg and corelevel excitations compared to the widely used linearresponse timedependent density functional theory (TDDFT) formalism. However, widespread application in excitedstate geometry optimization and molecular dynamics is hindered by limitations of standard selfconsistent field (SCF) algorithms. Such algorithms perform well in calculations of nondegenerate ground states (minima of the energy functionals) but commonly fail to converge excitedstate solutions because the latter are typically saddle points and are often nearly degenerate to each other or the ground state. To overcome this impediment we develop robust direct orbital optimization methods for variational excitedstate DFT calculations [13]. It will be shown how a novel approach using quasiNewton algorithms that can develop negative Hessian eigenvalues in combination with the maximum overlap method can converge excited states in molecules where conventional SCF approaches usually fail, such as chargetransfer excitations in nitrobenzene [13]. The new method can be used to calculate potential energy surfaces (PESs) of challenging electronically degenerate systems, as it will be shown for the double bond breaking and conical intesection in ethylene. There, unrestricted brokensymmetry solutions can provide PESs in agreement with multireference calculations. Challenges for application in excitedstate structural optimization or dynamics arise due to the presence of lower symmetry solutions with unphysical PESs. It will be illustrated how these issues can be overcome using strategies based on following the lowest eigenmodes of the electronic Hessian to converge on the target excitedstate solutions [4]. 
Wednesday, March 16, 2022 5:12PM  5:24PM 
Q01.00010: Beyond KohnSham DFT by including explicit orbital density dependence Hannes Jonsson Many shortcomings of practical implementations of KohnSham DFT can be traced to selfinteraction error that is introduced when the classical Coulomb interaction is estimated from total electron density. A more accurate estimate includes only the interaction of an orbital density with the density of other orbitals, thereby introducing explicit orbital density dependence (ODD). While shortcomings of KSDFT functional calculations are often ascribed to 'highcorrelation', the root of the problem can in some cases be due this singleelectron selfinteraction. One example of such a system is the manganese dimer, Mn2. Calculations at the generalized gradient approximation (GGA) and metaGGA level give qualitatively incorrect results with the bond energy overestimated by nearly 1 eV and bond length underestimated by about 1 A in a ferromagnetic ground state. However, calculations including PerdewZunger selfinteraction correction, which brings in an ODD functional form, give antiferromagnetic ground state and the results are in close agreement with both experimental observations and high level quantum chemistry calculations [1]. The shortcoming of the GGA and metaGGA functionals can be understood from analysis of the atomic and molecular orbitals. Similarly, the balance between localized and delocalized electronic states in diamine molecular cations [2] and electronic holes in oxides (such as Al substituted SiO2 and Li substituted MgO) [3] are well represented with an ODD functional while GGA and metaGGA functionals as well as commonly used hybrid functionals (with less than 50% exact exchange) fail to produce the localized states. The energy of excited electronic states of molecules is also better reproduced with ODD form [4]. By extending the functional form beyond that of KSDFT and allowing for explicit ODD in the energy functional, selfinteraction can be avoided and the accuracy of calculated results improved significantly. 
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