Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session W01: Density Functional Theory and Beyond VIIFocus Recordings Available

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Sponsoring Units: DCP Chair: Antonio Cancio, BSU Room: McCormick Place W175A 
Thursday, March 17, 2022 3:00PM  3:36PM 
W01.00001: SteadyState Density Functional Theory for Correlated Quantum Transport and Spectral Functions Invited Speaker: Gianluca Stefanucci SteadyState Density Functional Theory (iDFT) is a formalism to describe open quantum systems in nonequilibrium steady states. iDFT is based on the onetoone correspondence between the pair density and steady current and the pair local potential and applied voltage. The resulting KohnSham system features two exchangecorrelation (xc) potentials, a local xc potential and an xc contribution to the voltage. After revisiting the fundamentals of iDFT we apply the formalism to correlated quantum dots in the Coulomb blockade regime. We show that the wellknown discontinuity of the DFT xc potential at integer particle number bifurcates at finite currents. The iDFT formalism can also be used to calculate bulk spectral functions. We present an approximation to the xc voltage suited to describe a paradigm in the field of strongly correlated electrons, i.e., the Mott metalinsulator transition. 
Thursday, March 17, 2022 3:36PM  3:48PM 
W01.00002: Modelling the plateaus in the KohnSham and Pauli potentials Eli Kraisler, Axel Schild Density functional theory (DFT) is the leading theoretical framework used to describe electronic structure of materials. The most common approach in DFT is that of Kohn and Sham describes a material – a system of N interacting electrons – via a fictitious system of N noninteacting electrons subject to an effective potential termed the KohnSham (KS) potential. The KohnSham (KS) potential – a central quantity DFT – is known to build up plateaus and exhibit sharp spatial steps when describing the processes of dissociation, ionization, excitation and charge transfer. In this talk we show that the Pauli potential – a central quantity in orbitalfree DFT (OFDFT) and in the exact electron factorization (EEF) method – exhibits plateaus and steps, as well. We find the height of the plateau that builds up as a result of electron addition, we examine which terms of the Pauli potential contribute to the plateau (and which aren’t) and finally we model the spatial form of the plateau function. We back up our analytical findings by numerical examples. Our detailed analysis of the Pauli potential sheds light also on the step structure of the KS potential, which we discuss in our talk. 
Thursday, March 17, 2022 3:48PM  4:00PM 
W01.00003: Relativistic orbitaloptimized density functional theory for corelevel spectroscopy Leonardo dos Anjos Cunha, Richard Kang, Diptarka Hait, Martin P HeadGordon Xray spectroscopy is widely used to study local chemical environments by probing the electronic structure of the innermost orbitals and obtaining element specific spectral signatures. Theory can assist in interpreting these features, but accurate modelling requires a description of orbital relaxation effects that are crucial for characterizing the corehole. Moreover, as we explore elements of the periodic table with higher atomic numbers, relativistic effects become more relevant, especially for the prediction of K (1s) and L (2p) shell transitions. We combine orbitaloptimized (OO) DFT with the spinfree exact twocomponent one electron model (SFX2C1e) for scalar relativistic effects, to study Kedge XRay spectroscopies for elements of the third row and early transition metals of the periodic table. Our results show that the optimal protocol to simulate such effects is obtained when the SCAN density functional approximation is used with a local basis set that is flexible enough to describe the effects of orbital relaxation on the center of interest, predicting coreexcitation energies to < 0.5 eV RMSE error for a wide range of molecules containing third row main group elements. We also present progress on the simulation of transition metal Ledges within this framework. 
Thursday, March 17, 2022 4:00PM  4:12PM 
W01.00004: The Exponential Ansatz in the Context of Density Functional Theory: Elimination of Fractional Charges and Implications for Optical Excitations Martin A Mosquera The exponentialansatz operator is traditionally applied within coupled cluster theory to compute relatively accurate wave functions and related electronic properties of molecular systems. One of the most advantageous properties of this operator is its ability to offer sizeconsistent quantum methods. Motivated by such property, we discuss the application of this operator to density functional calculations. We show the adapted (nonHermitian) coupledcluster variational method and the exponential ansatz can eliminate (spurious) fractional charges for spinsymmetrybroken heterogenous molecular systems, whereas preserving a strong consistency with KohnSham LDA calculations in cases where these perform reasonably well. For linearresponse TDDFT calculations we show the exponential operator can also assist in the description of avoidedcrossing regions, and the study of quantum states where multiple electrons are optically excited. Finally, we discuss the role of the selfinteraction error in our methods involving the exponential operator. 
Thursday, March 17, 2022 4:12PM  4:48PM 
W01.00005: Incorporating Nuclear Quantum Effects in Molecular Dynamics Simulations with Multicomponent Density Functional Theory Invited Speaker: Yang Yang Nuclear quantum effects play an important role in a variety of chemical and biological processes and substantially affect many fundamental properties of systems involving hydrogen atoms. However, the accurate inclusion of nuclear quantum effects remains a significant challenge for largescale molecular simulations. We present an alternative formulation of equations of motion for molecular dynamics (MD) based on a constrained minimized energy surface (CMES). Since CMES inherently includes nuclear quantum effects, the resulting CMESMD is able to capture nuclear quantum effects such as quantum delocalization effects and tunneling effects. In model systems, CMESMD gives results that are comparable to or better than those from centroid molecular dynamics and ringpolymer molecular dynamics. In practical molecular systems, CMES can be obtained from constrained nuclearelectronic orbital density functional theory (cNEODFT), a multicomponent density functional theory that was recently developed in our group. The resulting cNEOMD is employed to calculate the vibrational spectra of a series of small molecules and the results are compared to those from conventional ab initio molecular dynamics (AIMD) as well as from experiments. With the same formal computational scaling, cNEOMD greatly outperforms AIMD in describing the vibrational modes with a significant hydrogen motion character, indicating the importance of nuclear quantum effects in molecular simulations. This work opens the door to the accurate and efficient simulation of chemical and biological systems with significant nuclear quantum effects using cNEOMD. 
Thursday, March 17, 2022 4:48PM  5:00PM 
W01.00006: Reliable lattice dynamics from an efficient density functional Jianwei Sun, James W Furness, Jinliang Ning First principles predictions of lattice dynamics are of vital importance for a broad range of topics in materials science and condensed matter physics. The largescale nature of lattice dynamics calculations and the desire to design novel materials with distinct properties demands that first principles predictions are accurate, transferable, efficient, and reliable for a wide variety of materials. In this work, we demonstrate that the recently constructed r2SCAN density functional meets this need for general systems by demonstrating phonon dispersions for typical systems with distinct chemical characteristics. The functional's performance opens a door for phononmediated materials discovery from first principles calculations. 
Thursday, March 17, 2022 5:00PM  5:12PM 
W01.00007: First principles binding energy evaluation of hostguest inclusion complexes Kenji Oqmhula, Kenta Hongo, Ryo Maezono, Tom Ichibha Molecular capsulation is a key technique for biopharmaceuticals. The development of molecular capsules from the theory side requires a precise evaluation of binding energy between capsules and biopharmaceutical molecules. For this purpose, density functional theory (DFT) is a suitable evaluation method due to its good balance of calculation accuracy and cost. However, it is not straightforward to accurately evaluate van der Waals and exchange interactions using a pure exchangecorrelation functional. Meanwhile, empirical corrections are known to significantly improve the accuracy. In this work, we benchmark CAM and D3 corrections applied to the B3LYP functional for the binding energy between plumbagin and cyclodextrins (βcyclodextrin/methylβcyclodextrin/2Ohydroxypropylβcyclodextrin). We calculate the reference binding energy by diffusion Monte Carlo (DMC) method. DMC accurately evaluates dispersion force without any practical approximations, unlike DFT. Both B3LYP and CAMB3LYP give almost zero binding energies (i.e., do not reproduce binding). On the other hand, B3LYPD3 and CAMB3LYPD3 give similar binding energies to DMC due to the D3 correction [1]. In this talk, we will also discuss the solvent effects on the binding energies. 
Thursday, March 17, 2022 5:12PM  5:24PM 
W01.00008: Diffusion Monte Carlo Study on Relative Stabilities of Boron Nitride Polymorphs Yutaka Nikaido, Tom Ichiba, Kenta Hongo, Fernando A Reboredo, Ryo Maezono, Kousuke Nakano One of the most fundamental properties of boron nitride (BN), the phase diagram, is still under debate both theoretically and experimentally even though BN compounds have wellknown industrial applications. The determination of the most stable BN's polymorph (hexagonal, rhombohedral, wurtzite, and zincblende) is difficult with abinitio methods because subtle vdW interactions are relevant in some of the polymorphs. This makes quantitative calculations challenging. As a result, despite significant theoretical research, there is no consensus yet on the most stable structure. There are several contradicting theoretical reports. We applied one of the stateoftheart abinitio methods, fixednode diffusion Monte Carlo (FNDMC), to the four known BN's polymorphs. We also performed phonon calculations to investigate thermal stability. Our FNDMC calculations showed that hexagonal BN is the most stable among the four polymorphs at 0 K. Our calculations of the contribution of phonons to the free energy confirmed that this is the case even at 300K. We compared our results to previous sophisticated studies such as MBD, RPA, RPAx, and CCSD(T). We found that RPAx and CCSD(T) are consistent with our FNDMC, whereas MBD and RPA are not. 
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