Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session T01: Density Functional Theory and Beyond VIFocus Recordings Available
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Sponsoring Units: DCP Chair: Adam Wasserman, Purdue Room: McCormick Place W-175A |
Thursday, March 17, 2022 11:30AM - 12:06PM |
T01.00001: What does it take to run orbital-free (TD)DFT and embedding simulations? And what do we get from them? Invited Speaker: Michele Pavanello This talk discusses orbital-free DFT and DFT embedding methods. Both rely on pure density functionals for the noninteracting kinetic energy, exchange and correlation. When venturing to nonequilibrium processes, semiquantitative to quantitative agreement with reality can only be achieved if nonadiabaticity and nonlocality is accounted for. Upon inclusion of nonlocality, embedding simulations reach a sub-kcal/mol accuracy in the inter-subsystem interactions dramatically widening the applicability of DFT to large system sizes. When nonadiabaticity is included in the Pauli potential, orbital-free TDDFT can be used to compute optical spectra and electron dynamics of metal and semiconductor systems with confidence in the usefulness of the results. The talk also touches upon best practices to realize efficient computer software encoding DFT embedding and orbital-free (TD)DFT and how to train the next generation of DFT software developers. |
Thursday, March 17, 2022 12:06PM - 12:18PM |
T01.00002: Nonlocal and Nonadiabatic Time-dependent Pauli Potential Kaili Jiang, Xuecheng Shao, Michele Pavanello Time-dependent orbital-free density functional theory (TD-OFDFT) is an efficient ab-initio method for calculating the electronic dynamics of large systems. In comparison to standard TD-DFT, it computes only a single electronic state regardless of system size, but it requires an additional time-dependent Pauli potential term. Based on the frequency-dependent Pauli kernel of the free electron gas, we propose a nonadiabatic and nonlocal Pauli potential as a functional of the time-dependent particle and current densities. Our calculations of the optical spectra of metallic and semiconductor clusters indicate that nonlocal and nonadiabatic TD-OFDFT performs accurately for metallic systems and semiquantitatively for semiconductors. This work opens the door to wide applicability of TD-OFDFT for nonequilibrium electron and electron-nuclear dynamics of materials. |
Thursday, March 17, 2022 12:18PM - 12:30PM |
T01.00003: Investigation of cusps and steps in the non-additive kinetic potential functional Vnad from analytic inversion Tim Gould, Leeor Kronik, David A Strubbe, Mojdeh Banafsheh The non-additive kinetic potential functional Vnad is a key issue in density-dependent embedding methods, such as Frozen Density Embedding Theory and Partition-DFT. Vnad is a bifunctional of pair of electron densities ρA and ρB. We previously reported the exact analytical inversion procedure to generate reference Vnad for weakly overlapping ρA and ρB(M. Banafsheh, T. A. Wesolowski, Int. J. Quant. Chem. 118 (2018): e25410). The behaviour of Vnad at the vicinity of the nuclei has been questioned since the beginning. Available computational tools and methods in the past led to a cusp at nuclei in Vnad calculations. We analyse existence and non-existence properties of the cusp in Vnad analytically, and compare against nuclear cusps condition for the ground-state density and resulting cusp in the Kohn-Sham potential. We show the agreement of numerical calculations with this fact for various diatomic model systems of two and four electrons. The results are compared to the von Weizsäcker functional (exact for one orbital) and other kinetic energy functionals. |
Thursday, March 17, 2022 12:30PM - 12:42PM |
T01.00004: Consistent deorbitalization and new deorbitalizers for meta-GGA exchange-correlation functionals Hector I Francisco Rodriguez, Samuel B Trickey, Antonio C Cancio A key challenge for use of Kohn-Sham density functional theory is to improve the quality and accuracy of low-computational cost exchange-correlation (XC) density functional approximations (DFAs). De-orbitalization, the replacement of the KS kinetic energy density in a meta-GGA with an explicit function of n(r), its gradient, and its laplacian, is a recently successful approach with the SCAN and r2SCAN DFAs [Phys. Rev. A 96, 052512 (2017); Phys. Rev. B 102, 121109 (2020)]. Their procedure was not entirely consistent. Here we reparametrize the α switching function consistently with the atomic densities of the parent DFAs. The result is almost indistinguishable from the original: slight improvements on heats of formation (G3/99X), bond lengths (T96-R), and vibration frequencies (T82-F). We also have extended consistent deorbitalization to the original, regularized, and revised regularized Tao-Mo DFAs [Phys. Rev. Letter. 117, 073001 (2016); J. Chem. Phys. 153, 184112 (2020); J. Chem. Phys. 155, 024103 (2021)] with good results. |
Thursday, March 17, 2022 12:42PM - 12:54PM |
T01.00005: Two-Orbital Approximation for Partition Density Functional Theory Victor Hugo Gonzalez Chavez, Yan Oueis, Adam Wasserman Partition Density Functional Theory (P-DFT) is an embedding method in which molecular properties are computed through calculations on the molecule’s constituents. The lack of an accurate approximation for the non-interacting kinetic energy functional in terms of the set of fragment densities makes practical P-DFT calculations a challenge. We have shown that a simple expression for the non-additive kinetic energy based on a “two-orbital approximation” (2OA) reproduces extremely well the large-R asymptotic behavior of the dissociation energy of rare-gas dimers with internuclear separation R. We discuss here the physical motivation behind the construction of the 2OA, its limitations, and how we are extending it to make it more applicable to a broader class of molecules. |
Thursday, March 17, 2022 12:54PM - 1:06PM |
T01.00006: Deriving Corrections to the 1D TF Kinetic Energy Functional: The first step towards a systematic DFT Pavel Okun, Kieron Burke Recent developments have shown that density functionals can be derived from semiclassical quantum mechanics in a systematic fashion reminiscent of wavefunction electronic structure. This new technique is completely different from other approaches to functional design (such as the satisfaction of exact conditions or fitting empirical parameters). The Thomas-Fermi kinetic energy functional, which Lieb and Simon showed is exact in the semiclassical limit, is the lowest order term in a semiclassical expansion of the exact kinetic energy functional. We will show, at least in one dimension, how higher order corrections to this series can be obtained by calculating the sums of eigenvalues and then inverting these sums into density functionals. Thus we show how to generate the exact asymptotic expansion of the true kinetic energy functional. We will also demonstrate that boundary terms arise from the turning points/surfaces where the density cannot be slowly varying, which are missed by the traditional gradient expansion. To simplify our analysis we have worked in 1D but we shall comment on the application of our work to real electronic systems and show some preliminary results on simple 3D systems. |
Thursday, March 17, 2022 1:06PM - 1:18PM |
T01.00007: Suppressing exchange-correlation errors through a Generalized Overlap Approximation in Partition-DFT Yuming Shi, Adam Wasserman Quantum embedding methods can in principle lead to linear scaling and multilevel-accuracy calculations of electronic properties of molecules and materials. Partition Density Function Theory (P-DFT), a density-based embedding method, features a unique interaction potential and in many cases fragments with fractional numbers of electrons. An "overlap approximation" (OA) for the partition energy of P-DFT has been shown to eliminate errors caused by the underlying exchange-correlation approximations, such as delocalization and static-correlation errors, even when using the Local Density Approximation for the fragments. Although the initial formulation of the OA was applicable only to small homonuclear diatomic molecules, we have revised its derivation and demonstrated its applicability to larger, less symmetric systems. |
Thursday, March 17, 2022 1:18PM - 1:30PM |
T01.00008: Visualizing and testing orbital free models of the kinetic energy density in semiconductors Antonio C Cancio, Akinfolarin Akinola, Brielle Shope
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Thursday, March 17, 2022 1:30PM - 1:42PM |
T01.00009: Variational optimization of Pauli potentials for orbital-free density functional theory Antonio C Cancio, Bishal Thapa The goal of Orbital-Free Density Functional Theory is to model the Kohn-Sham noninteracting kinetic energy as a functional of ingredients derived from the density directly, so as to remove the bottleneck of computing orbitals in large systems. The Perdew-Constantin KE meta-GGA [1] and later improvements [2] use the Laplacian of the density to switch from the slowly varying electron gas to the von Weizsacker or single electron-pair limits. While producing an accurate KE density, that use of the density Laplacian creates unphysically spiky Pauli potentials that are numerically difficult to solve and lead to noisy results. To ameliorate this problem, we construct and test a smoothness measure based on the variational description of Poisson's equation, applied to the Laplacian-generated terms in the potential. Optimization of PC-like models with respect to this measure under the constraint of preserving the total kinetic energy can substantially but not completely remove unphysical features in the Pauli potentials of small atoms. We discuss prospects for using the result in deorbitalized meta-GGA functionals. |
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