Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session J58: DFT and Beyond VIFocus
|
Hide Abstracts |
Sponsoring Units: DCP DCOMP DPOLY DCMP Chair: Sahar Sharifzadeh, Boston Univ Room: Mile High Ballroom 3B |
Tuesday, March 3, 2020 2:30PM - 3:06PM |
J58.00001: Steady-State Density Functional Theory for quantum transport and spectral functions Invited Speaker: Gianluca Stefanucci Steady-State Density Functional Theory (i-DFT) is a formalism to describe open quantum systems in nonequilibrium steady states. i-DFT is based on the one-to-one correspondence between the pair density and steady current and the pair local potential and applied voltage. The resulting Kohn-Sham system features two exchange-correlation (xc) potentials, a local xc potential and an xc contribution to the voltage. After revisiting the fundamentals of i-DFT we apply the formalism to strongly correlated quantum dots at finite current and temperature. We show that the well-known discontinuity of the DFT xc potential at integer particle number bifurcates as the current starts flowing. We also show that the i-DFT formalism can be used to calculate the quantum system spectral function, a relevant quantity in photoemission spectroscopy. |
Tuesday, March 3, 2020 3:06PM - 3:18PM |
J58.00002: Linearized GW density matrix for molecules Fabien Bruneval The GW approximation is well known for the calculation of high-quality ionization potentials and electron affinities in solids and molecules. However, the Green's function contains much more information than the mere quasiparticle energies. |
Tuesday, March 3, 2020 3:18PM - 3:30PM |
J58.00003: Dynamical excitations of charge states in diamond color centers Tatiane Pereira Dos Santos, Andre Schleife We perform a time-dependent computational study of nitrogen-vacancy centers in diamond under ion irradiation. The negatively charged nitrogen-vacancy (NV-) centers in diamond are potential candidates for solid-state qubits due to the possibility to manipulate single center's electronic spin states. However, the dynamics of charge transitions between NV centers of different charges, such as the neutral (NV0) and the positively charged (NV+) centers, are not fully understood. Using time-dependent ab initio calculations, we perform accurate dynamical simulations of ion projectiles propagating near NV centers in diamond and calculate the properties of the defect-related excited states under the projectile impact. We compare our results with a pristine diamond and calculate the dynamical properties of projectile-vacancy coupling for a set of ion projectiles at different velocities. We discuss the quantitative properties of the charge states of nitrogen-vacancy centers at a sufficiently short time-scale that are challenging to approach experimentally. |
Tuesday, March 3, 2020 3:30PM - 3:42PM |
J58.00004: Recent progress in the first-principles quantum Monte Carlo: New algorithms in the all-electron calculations Kosuke Nakano, Ryo Maezono, Sandro Sorella First-principles quantum Monte Carlo (QMC) techniques, such as variational quantum Monte Carlo (VMC) and diffusion quantum Monte Carlo (DMC), are among the state-of-the-art numerical methods used to obtain highly accurate many-body wave functions. I will present recent improvements in a QMC code, TurboRVB: All-electron calculations in QMC are not as widely used as in DFT because the computational cost scales with Z5.5−6.5, where Z is the atomic number. We have recently developed new algorithms to drastically decrease computational costs of all-electron DFT (suitable for QMC)[1], and all-electron lattice regularized diffusion monte Carlo (LRDMC)[2,3]. I will present basic ideas of the new algorithms and show several applications such as a binding energy calculation of the sodium dimer[1]. |
Tuesday, March 3, 2020 3:42PM - 3:54PM |
J58.00005: Thermo-Optical Properties of Organic Verdazyl Biradicals via UV-VIS Spectroscopy Ozge Gunaydin-Sen, Caitlyn Clark, Emily Ingram, David Brook Recently, biradicals have attracted attention due to their magnetic properties which could be used in different fields such as electronics, computer technologies, and renewable energy. Unlike most of the other radicals, organic verdazyl biradicals are stable at room temperature which makes them easy to work with. We investigated the photo-physical properties (i.e. singlet-triplet spin gap) of verdazyl biradicals utilizing thermo-optical spectroscopy (UV-VIS) between room temperature and 400 K.The spectra were then analyzed using Beer’s law and Curie population analysis to extract the singlet-triplet spin gap at several wavelengths by evaluating the excitations. The analysis suggests, stronger excitations are representative of π→π* transitions while the weaker excitations are representative of forbidden π→π* transitions. Switching between singlet ground and triplete excited states can lead to an improved understanding of the manipulation via change in temperature and possibly with the magnetic field. |
Tuesday, March 3, 2020 3:54PM - 4:06PM |
J58.00006: Perdew-Zunger self-interaction correction: How wrong for uniform densities and large-Z atoms? Biswajit Santra, John P. Perdew Semilocal exchange-correlation (xc) energy of a many-electron system is not exact for all one-electron densities. In 1981, Perdew and Zunger (PZ) subtracted the fully nonlocal self-interaction error orbital-by-orbital, making the corrected functional exact for all one-electron densities. Although the PZ self-interaction correction (SIC) eliminates many errors of semilocal functionals, it is often worse for equilibrium properties of molecules and solids. Nonempirical semilocal functionals are usually designed to be exact for uniform electron gases, but PZ SIC is not so designed. We have extrapolated from the Ne, Ar, Kr, and Xe atoms to estimate the relative errors of the PZ SIC xc energies (with localized SIC orbitals) in the limit of large atomic number: about +5.5% for the LSDA-SIC and about -3.5% for nonempirical generalized gradient (PBE)-SIC and meta-generalized gradient strongly constrained and appropriately normed (SCAN)-SIC approximations [1]. The SIC errors found here are considerably larger than the error previously estimated on the uniform gas using LSDA-SIC localized orbitals. These errors may explain the shortcomings of PZ SIC for equilibrium properties, opening the path to a generalized SIC. |
Tuesday, March 3, 2020 4:06PM - 4:18PM |
J58.00007: Constrained optimization of Fermi-orbital descriptors Kai Trepte, Juan Peralta, Koblar Alan Jackson The Fermi-Löwdin orbital self-interaction correction (FLO-SIC) method removes the spurious self-interaction from common density functional theory (DFT) approximations. Within FLO-SIC, Fermi orbitals are used as localized orbitals. Each of these orbitals is constructed using a point in real space, called Fermi-orbital descriptor (FOD). To obtain the minimum total energy, the set of FODs needs to be optimized. |
Tuesday, March 3, 2020 4:18PM - 4:30PM |
J58.00008: New Algorithms for the Fermi-Löwdin Orbital Self-Interaction Correction Calculations. Kamal Sharkas, Juan E Peralta, Koblar Jackson Self--interaction error (SIE) is in most approximate exchange-correlation functionals, and removing SIE is important for improving the performance of the Kohn-Sham density-functional theory (KS-DFT) when applied to systems of chemical and physical interest. The Fermi-Löwdin Orbital Self-Interaction Correction (FLO-SIC) methodology was recently introduced as a unitarily invariant reformulation of the Perdew-Zunger SIC scheme to remove unphysical SIE from DFT. |
Tuesday, March 3, 2020 4:30PM - 4:42PM |
J58.00009: Perdew-Zunger Self-Interaction Correction in Neutral, Protonated, and Deprotonated Water Clusters Kamal Wagle, Biswajit Santra, Kamal Sharkas, Sharmin Akter, Rajendra R Zope, Tunna Baruah, Koblar Jackson, Juan E Peralta, John P. Perdew We have assessed the importance of self-interaction correction (SIC) to density functional approximations (DFA) for the description of water-ion interactions. We have used LSDA, PBE, SCAN, and the Fermi-Löwdin orbital self-interaction correction (FLOSIC)1 in conjunction with these DFAs to calculate the binding energies of neutral, protonated [H3O+(H2O)n], and deprotonated [OH-(H2O)n] water clusters, where n denotes the number of water molecules. Including SIC is important to obtain accurate binding energies for these clusters. We find that FLOSIC-SCAN not only improves the mean absolute error in the binding energy of all clusters but also preserves the energetic ordering of the low-lying water hexamers (prism, cage, book, and cyclic) that was difficult to achieve with many non-empirical DFAs. Moreover, many-body decomposition of the total binding energy reveals that FLOSIC-SCAN significantly reduces the two-body errors in SCAN calculations. The three-body and higher-order many-body errors are also small with FLOSIC-SCAN. This shows that FLOSIC-SCAN has the potential to overcome the limitations of SCAN in describing water and aqueous ions in condensed phases. |
Tuesday, March 3, 2020 4:42PM - 4:54PM |
J58.00010: Study of water cluster anions using the self-interaction corrected density functional approximations Jorge Vargas, Peter Ufondu, Tunna Baruah, Koblar Alan Jackson, Rajendra Zope Accurate description of the excess charge in water cluster anions is challenging for standard semi-local and (global) hybrid density functional approximations (DFAs). Using the recent unitary invariant implementation of the Perdew-Zunger self-interaction correction (SIC) method by means of Fermi-Lowdin orbitals, we assess the effect of self-interaction error on the vertical detachment energies (vDEs) of water cluster anions with the local spin density approximation (LSDA), PBE-GGA, and the SCAN meta-GGA functionals. Removal of self interaction error corrects the electron overbinding tendency of the LSDA, PBE, and SCAN. The vDEs of water cluster anions, obtained from the total energy difference of anion and neutral, are significantly improved upon removal of self-interaction errors and are better than the hybrid B3LYP functional but fall short of MP2 accuracy. Removal of SIE results in substantial improvement to the eigenvalue of the extra electron. The negative of the highest occupied eigenvalue after SIC provides an excellent approximation to the vertical detachment energy especially for the SIC-PBE wherein the MAE of vDEs with respect to CCSD(T) is only 17 meV, the best amongst all approximations compared in this work. |
Tuesday, March 3, 2020 4:54PM - 5:06PM |
J58.00011: Fermi-Lowdin orbital self-interaction corrections applied to water clusters: Polarizabilities, dipole moments, and ionization energies Sharmin Akter, Yoh Yamamoto, Rajendra Zope, Tunna Baruah The self-interaction (SI) error in density functional approximations (DFA) often leads to excessive delocalization of electron density. We examine the effect of self-interaction correction on the static dipole polarizabilities of small water clusters (H2O)n for n=1-6 using the Fermi-Lowdin self-interaction correction (FLOSIC) method. The static polarizability of a molecule determines its response to an applied static electric field. Density functional approximations generally overestimate the polarizabilities of molecules and atoms which is found to be improved by incorporation of SI correction. The polarizabilities of the water clusters are calculated with DFAs at the local, generalized gradient and meta-GGA levels. Previously optimized geometries at the CCSD(T) level are used for this calculation. Results show that the lower level approximations, LDA and GGA, overestimate the polarizability values whereas FLOSIC corrects the polarizabilities leading to better agreement with reference CCSD(T) values. We also investigate the effect of removing the self-interaction error on the dipole moments and ionization potentials of these clusters with different functionals. The results will be presented and discussed. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700