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

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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: SteadyState Density Functional Theory for 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 strongly correlated quantum dots at finite current and temperature. We show that the wellknown discontinuity of the DFT xc potential at integer particle number bifurcates as the current starts flowing. We also show that the iDFT 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 highquality 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 timedependent computational study of nitrogenvacancy centers in diamond under ion irradiation. The negatively charged nitrogenvacancy (NV^{}) centers in diamond are potential candidates for solidstate 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 (NV^{0}) and the positively charged (NV^{+}) centers, are not fully understood. Using timedependent ab initio calculations, we perform accurate dynamical simulations of ion projectiles propagating near NV centers in diamond and calculate the properties of the defectrelated excited states under the projectile impact. We compare our results with a pristine diamond and calculate the dynamical properties of projectilevacancy coupling for a set of ion projectiles at different velocities. We discuss the quantitative properties of the charge states of nitrogenvacancy centers at a sufficiently short timescale that are challenging to approach experimentally. 
Tuesday, March 3, 2020 3:30PM  3:42PM 
J58.00004: Recent progress in the firstprinciples quantum Monte Carlo: New algorithms in the allelectron calculations Kosuke Nakano, Ryo Maezono, Sandro Sorella Firstprinciples quantum Monte Carlo (QMC) techniques, such as variational quantum Monte Carlo (VMC) and diffusion quantum Monte Carlo (DMC), are among the stateoftheart numerical methods used to obtain highly accurate manybody wave functions. I will present recent improvements in a QMC code, TurboRVB: Allelectron calculations in QMC are not as widely used as in DFT because the computational cost scales with Z^{5.5−6.5}, where Z is the atomic number. We have recently developed new algorithms to drastically decrease computational costs of allelectron DFT (suitable for QMC)[1], and allelectron 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: ThermoOptical Properties of Organic Verdazyl Biradicals via UVVIS Spectroscopy Ozge GunaydinSen, 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 photophysical properties (i.e. singlettriplet spin gap) of verdazyl biradicals utilizing thermooptical spectroscopy (UVVIS) between room temperature and 400 K.The spectra were then analyzed using Beer’s law and Curie population analysis to extract the singlettriplet 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: PerdewZunger selfinteraction correction: How wrong for uniform densities and largeZ atoms? Biswajit Santra, John P. Perdew Semilocal exchangecorrelation (xc) energy of a manyelectron system is not exact for all oneelectron densities. In 1981, Perdew and Zunger (PZ) subtracted the fully nonlocal selfinteraction error orbitalbyorbital, making the corrected functional exact for all oneelectron densities. Although the PZ selfinteraction 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 LSDASIC and about 3.5% for nonempirical generalized gradient (PBE)SIC and metageneralized 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 LSDASIC 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 Fermiorbital descriptors Kai Trepte, Juan Peralta, Koblar Alan Jackson The FermiLöwdin orbital selfinteraction correction (FLOSIC) method removes the spurious selfinteraction from common density functional theory (DFT) approximations. Within FLOSIC, Fermi orbitals are used as localized orbitals. Each of these orbitals is constructed using a point in real space, called Fermiorbital 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 FermiLöwdin Orbital SelfInteraction Correction Calculations. Kamal Sharkas, Juan E Peralta, Koblar Jackson Selfinteraction error (SIE) is in most approximate exchangecorrelation functionals, and removing SIE is important for improving the performance of the KohnSham densityfunctional theory (KSDFT) when applied to systems of chemical and physical interest. The FermiLöwdin Orbital SelfInteraction Correction (FLOSIC) methodology was recently introduced as a unitarily invariant reformulation of the PerdewZunger SIC scheme to remove unphysical SIE from DFT. 
Tuesday, March 3, 2020 4:30PM  4:42PM 
J58.00009: PerdewZunger SelfInteraction 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 selfinteraction correction (SIC) to density functional approximations (DFA) for the description of waterion interactions. We have used LSDA, PBE, SCAN, and the FermiLöwdin orbital selfinteraction correction (FLOSIC)^{1} in conjunction with these DFAs to calculate the binding energies of neutral, protonated [H_{3}O^{+}(H_{2}O)_{n}], and deprotonated [OH^{}(H_{2}O)_{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 FLOSICSCAN not only improves the mean absolute error in the binding energy of all clusters but also preserves the energetic ordering of the lowlying water hexamers (prism, cage, book, and cyclic) that was difficult to achieve with many nonempirical DFAs. Moreover, manybody decomposition of the total binding energy reveals that FLOSICSCAN significantly reduces the twobody errors in SCAN calculations. The threebody and higherorder manybody errors are also small with FLOSICSCAN. This shows that FLOSICSCAN 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 selfinteraction 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 semilocal and (global) hybrid density functional approximations (DFAs). Using the recent unitary invariant implementation of the PerdewZunger selfinteraction correction (SIC) method by means of FermiLowdin orbitals, we assess the effect of selfinteraction error on the vertical detachment energies (vDEs) of water cluster anions with the local spin density approximation (LSDA), PBEGGA, and the SCAN metaGGA 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 selfinteraction 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 SICPBE 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: FermiLowdin orbital selfinteraction corrections applied to water clusters: Polarizabilities, dipole moments, and ionization energies Sharmin Akter, Yoh Yamamoto, Rajendra Zope, Tunna Baruah The selfinteraction (SI) error in density functional approximations (DFA) often leads to excessive delocalization of electron density. We examine the effect of selfinteraction correction on the static dipole polarizabilities of small water clusters (H2O)n for n=16 using the FermiLowdin selfinteraction 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 metaGGA 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 selfinteraction error on the dipole moments and ionization potentials of these clusters with different functionals. The results will be presented and discussed. 
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