Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session N01: Density Functional Theory and Beyond IVFocus Recordings Available

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Sponsoring Units: DCP Chair: Carsten Ullrich, University of Missouri Room: McCormick Place W175A 
Wednesday, March 16, 2022 11:30AM  12:06PM 
N01.00001: Exciton diffusion from first principles: role of crystal packing and composition Invited Speaker: Sivan RefaelyAbramson Understanding excitedstate dynamics in functional materials is essential for applications across optoelectronics and photophysics. In particular, exciton diffusion and relaxation mechanisms are coupled to optical selection rules and can be tuned through atomistic design. In this talk, I will present our recent studies of exciton transport in functional materials, using ab initio computations based on manybody perturbation theory. Specifically, I will discuss the relation between exciton relaxation mechanisms with the underlying material structure and symmetry: molecular packing in organic crystals and defect and heterostructure design in transition metal dichalcogenides. I will present our new approach to compute exciton propagation, in which nonanalytical discontinuities in the exciton dispersion are connected to the early stages of exciton diffusion. I will further discuss our scheme to include excitonphonon interactions from first principles and the associated exciton diffusion lifetimes and pathways. 
Wednesday, March 16, 2022 12:06PM  12:18PM 
N01.00002: An optimal tuning perspective of rangeseparated doublehybrid functionals Michal Hartstein, Georgia Prokopiou, Niranjan Govind, Leeor Kronik We study the tuning of the free parameters of rangeseparated double hybrid functionals, based on the exact conditions of piecewise linearity and spin constancy. We find that introducing rangeseparation in both exchange and correlation allows for the minimization of both fractional charge and fractional spin errors for singlet atoms. The optimal set of parameters is system specific, underlining the importance of the tuning procedure. We use the tuned functionals to compute dissociation curves of diatomic molecules. We recover the correct dissociation curve for the oneelectron system, H_{2}^{+}.We also find improvement in the dissociation curves of H_{2} and Li_{2}, but they still exhibit a nonphysical maximum before approaching the correct dissociation limit at very large distances. 
Wednesday, March 16, 2022 12:18PM  12:30PM 
N01.00003: RangeSeparated Hybrid Functional Pseudopotentials Georgia Prokopiou, Yang Yang, Tian Qiu, Aaron Schankler, Andrew M Rappe, Leeor Kronik, Robert A Distasio Consistency between the exchangecorrelation functional used during pseudopotential construction and planewavebased electronic structure calculations is important for an accurate and reliable description of the structure and properties of condensedphase systems. In this work, we present a general scheme for generating pseudopotentials with rangeseparated hybrid (RSH) exchangecorrelation functionals, extending on previous work on global hybrids [1]. We demonstrate this approach using the nontrivial example of the Ti atom, and discuss the importance of pseudopotential consistency when describing a variety of different solidstate systems. 
Wednesday, March 16, 2022 12:30PM  12:42PM 
N01.00004: Rangeseparated van der Waals density functional hybrids Vivekanand Shukla, Yang Jiao, Carl M Frostenson, Per Hyldgaard Hybrid density functionals replace a fraction of an underlying exchange with a Fockexchange component. They are successful in accurately describing a wide range of molecular and bulk properties. Rangeseparated hybrids (RSHs) also effectively screen the Fockexchange component and thus open the door for characterizations of metals and of adsorption at metal surfaces. However, the inclusion of van der Waals (vdW) forces remains a challenge. We present a set of new RSHs within the framework of the vdW density functional (vdWDF) method and based on an analyticalhole description of their gradientcorrected exchange components^{1}. Our most robust design termed vdWDFahcx, is based on the consistentexchange vdWDFcx version that leverages a Lindhard screening argument to balance exchange and correlation^{2}. It is set up to describe the adsorption of molecules at general surfaces. We test the performance of our vdWDF RSHs on a broad set of molecular properties, bulk structure and cohesion, as well as bandgaps of semiconductors. Finally, we test the vdWDF RSHs on the longstanding CO adsorption puzzle and we discuss the results. 
Wednesday, March 16, 2022 12:42PM  12:54PM 
N01.00005: Band Gap Problem Caused by Widespread Errors in Calculations and not by Density Functional Theory (DFT) Yuriy Malozovsky, Diola Bagayoko, Yacouba I Diakite The second theorem of Density functional theory (DFT) is clear: To obtain results that possess the full, physical content of DFT, an electronic structure calculation must utilize the ground state charge density in order to reach the ground state energy. This threedimensional charge density is à priori unknown. Consequently, electronic structure calculations must perform a generalized minimization of the energy functional, using successive, selfconsistent calculations with augmented basis sets, to reach the absolute minima of the occupied energies, i.e., the ground state. Then, first or smallest of the basis sets that lead to the ground state produces the ground state charge density upon reaching selfconsistency. The mainstream practice of selecting a single basis set and of performing iterations to reach a stationary state mistakenly consider that state to be the ground state. We prove, with the Rayleigh theorem for eigenvalues and the second DFT theorem, that it is not. In doing so, we show that the widespread disagreement between the results of “DFT calculations” and corresponding experimental ones cannot be ascribed to DFT. With the correct, computational method, we have described and predicted electronic and related properties of 25 semiconductors, including their band gaps that were underestimated by 359 previous DFT calculations. 
Wednesday, March 16, 2022 12:54PM  1:06PM 
N01.00006: Quasiparticle band structures of halide double perovskites using Wannierlocalized optimally tuned screened range separated hybrid functionals Francisca Sagredo, Stephen E Gant, Guy Ohad, Jonah B Haber, Marina R Filip, Leeor Kronik, Jeffrey B Neaton Halide double perovskites are a promising new class of materials that offer an alternative to lead halide perovskites as suitable materials to use for solar cell applications, due to their greater stability and reduced susceptibility to environmental factors. Previous calculations of the band gaps using semilocal density functionals and the GW approximation, in conjunction with the lack of experimental data available for these class of materials, has left room for ambiguity in predicting the correct fundamental band gaps of these systems. Here we use the new state of the art, Wannierlocalized, optimally tuned screened range separated hybrid functional (WOTSRSH) which has recently been shown to be a promising approach for a range of standard semiconductors and insulators. We compare and discuss the band gaps and band structures for double perovskites we obtain with this method with prior theory and experiment. 
Wednesday, March 16, 2022 1:06PM  1:18PM 
N01.00007: Effect of Structural Defects on the Interaction of DNA Bases with Graphene Nanoribbons: van der Waals Corrected Density Functional Theory Calculations Benjamin O Tayo, Sagar Ghimire, Pujan Khatri, Sanjiv K Jha Graphene is a promising material for a wide range of applications including the sensing and sequencing of DNA nucleobases. In this study, we investigated the adsorption of four DNA nucleobases (adenine, guanine, thymine, and cytosine) on atomically thin armchair graphene nanoribbons (AGNRs) using density functional theory (DFT). The binding energies of the nucleobases on AGNRs were examined for AGNRs containing no surface defects, containing StoneWales (SW) defects, and containing divacancy (DV) defects. The geometry optimizations of the four DNA bases on AGNRs were performed using van der Waals corrected (vdWDF2 and semiempirical Grimme’sD2) DFT calculations. The DNA nucleobases showed different binding strengths on graphene, and their binding energies followed the order: G > A > T > C. The presence of structural defects on the AGNRs showed no significant change on the computed binding energies and band gaps of the DNA bases. 
Wednesday, March 16, 2022 1:18PM  1:30PM 
N01.00008: Van der Waals contributions in DFT calculations of cysteineAu adsorption Emiliano VenturaMacias, Ruben Perez Cysteine adsorption on Au surfaces, through its thiol group, is the primary mechanism for protein attachment on such surfaces. This bond is essential for developing proteinbased bioelectronic devices because of the broad use of gold as an electrodes. When designing these devices, simulations almost always require molecular dynamics methods, but quantum mechanics methods are still needed to describe adsorption energy accurately. Density Functional Theory, with different van der Waals schemes, has become a handy tool for simulating molecule adsorption while retaining the chemical accuracy of QM methods. In this work, we have compared how the energetics of SAu adsorption change with different DFT+vdW schemes. We found that PBE+DFTD3 could be the preferred option over newer methods like SCANrvv10 as it yields similar results at a smaller computational cost. Also, DFTD3 outperforms a specially modified version of DFTD2 for SAu adsorption, suggesting that the inclusion of the chemical environment in DFTD3 is crucial for accurate results. Lastly, we compared cysteine to alkanethiols with different chain lengths and found that the chemical part of adsorption remains the same while most of the change comes from the physical adsorption and is directly related to the molecule size. 
Wednesday, March 16, 2022 1:30PM  1:42PM 
N01.00009: Accurate noncovalent interactions from models for the MøllerPlesset adiabatic connection Stefan Vuckovic, Timothy J Daas, Eduardo Fabiano, Fabio Della Sala, Paola GoriGiorgi A range of failures of the secondorder Mo̷ller−Plesset perturbation theory (MP2) for noncovalent interactions (NCI) have been described in the literature [1,2]. Moreover, the whole MP series can be diverging for large noncovalent complexes [1]. Our model based on the MøllerPlesset (MP) adiabatic connection [35] fixes all these issues of MP2 at no extra cost [6]. In this talk, I will give a theoretical basis for these models, show results for specific classes of NCI complexes, and discuss strategies for further improvements. 
Wednesday, March 16, 2022 1:42PM  1:54PM 
N01.00010: Space warp coordinate transformation for efficient ionic force calculations in quantum Monte Carlo Kosuke Nakano, Abhishek Raghav, Sandro Sorella Although abinitio quantum Monte Carlo (QMC) groundstate energy calculation is standard and widely used in physics and chemistry, calculation of atomic forces is still under technical/algorithmic development. We have benchmarked the accuracy of allelectron variational Monte Carlo (VMC) and lattice regularized diffusion Monte Carlo (LRDMC) forces for various mono and heteronuclear dimers. The VMC and LRDMC forces were calculated with the socalled space warp coordinate transformation (SWCT) and appropriate regularization techniques to remove the infinite variance problem. We have found that the appropriate use of the SWCT transformation makes the calculation of forces very efficient and feasible also for large atomic number. This is a quite promising conclusion from the viewpoint of the application of QMC forces, opening the door for future important applications of QMC in electronic structure calculations. 
Wednesday, March 16, 2022 1:54PM  2:06PM 
N01.00011: Rational Design of SingleAtom Catalysts for Enhanced Electrocatalytic Nitrogen Reduction Reaction Sakshi Agarwal Electrocatalytic reduction of N_{2} to ammonia (eNRR) provides a sustainable alternative to an energyintensive Haber−Bosch process. However, the poor activity and selectivity of the eNRR catalysts limit their largescale applications. Recently, transition metals (TMs) doped graphitic carbon nitridebased singleatom catalysts (SACs) have emerged as a very promising class of catalysts. Inspired by their activity and selectivity for a range of reactions, using density functional theory we investigated TMs (3d, 4d, and 5d series) anchored on h C_{4}N_{3} as possible catalysts for eNRR. We employed a search scheme for finding an efficient TM SAC for eNRR, based on its optimum N_{2} adsorption, N_{2} protonation feasibility, and selectivity against HER. The optimum bond strength of TM−N bond is characterized by a change in the magnetic moment of the metal upon N_{2} adsorption, and the charge transferred (△q) from TM to N_{2} molecule. We also established the number of valence electrons (group number) of the TM as a potential descriptor to determine the feasibility of N_{2} protonation, which ultimately decides the activity and selectivity of an eNRR catalyst. SACs with TMs belonging to the groups 5−7 are found to have the highest activity. Mo and WSACs emerge as the most suitable candidates after the third level of screening, which is based on the selectivity toward eNRR. The overpotentials for both Mo and WSACs are 0.02 and 0.33 V versus SHE, respectively. The thermodynamic analysis suggests that Mobased SAC is the most active catalyst for eNRR with an ultralow overpotential and high faradaic efficiency for eNRR. Our analysis provides a rational design of a new class of highly efficient catalysts for the electrochemical NRR under ambient conditions. 
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