Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session G1: Recent Advances in Density Functional Theory III |
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Sponsoring Units: DCP DCOMP Chair: John P. Perdew, Temple University Room: 103/105 |
Tuesday, March 4, 2014 11:15AM - 11:51AM |
G1.00001: Insight into Structural Phase Transitions from Density Functional Theory Invited Speaker: Adrienn Ruzsinszky Structural phase transitions caused by high pressure or temperature are very relevant in materials science [1]. The high pressure transitions are essential to understand the interior of planets. Pressure or temperature induced phase transitions can be relevant to understand other phase transitions in strongly correlated systems or molecular crystals.\textbf{ }Phase transitions are important also from the aspect of method development [2,3,4]. Lower level density functionals, LSDA and GGAs all fail to predict the lattice parameters of different polymorphs and the phase transition parameters at the same time. At this time only nonlocal density functionals like HSE and RPA have been proved to resolve the geometry-energy dilemma to some extent in structural phase transitions [1]. In this talk I will report new results from the MGGA\textunderscore MS family of meta-GGAs and give an insight why this type of meta-GGAs can give a systematic improvement of the geometry and phase transition parameters together [3,4]. I will also present results from the RPA and show a possible way to improve beyond RPA.\\[4pt] [1] Xiao, B., Sun, J., Ruzsinszky, A., J. Feng, and Perdew, J.P.,\textit{ Phys. Rev. B} \textbf{2012,} 86, 094109.\\[0pt] [2] Ruzsinszky, A., Sun, J., Xiao, B., and Csonka G.I., \textit{J. Chem. Theory and Comp. }\textbf{2012}$, $8, 2078.\\[0pt] [3] Sun, J., Xiao, B., and Ruzsinszky, A., \textit{J. Chem. Phys.} \textbf{2012,} 137, 051101.[4] Sun, J., Xiao, B., Fang, Y., Hao, P., Ruzsinszky, A., et al., \textit{Phys. Rev. Lett.} \textbf{2013}, 111, 106401. [Preview Abstract] |
Tuesday, March 4, 2014 11:51AM - 12:03PM |
G1.00002: New ways of computing effective potentials for orbital-dependent functionals Viktor N. Staroverov Orbital-dependent density functionals offer many advantages over local-density and gradient-corrected approximations, but also pose distinctive challenges to developers and users alike. In particular, evaluation of functional derivatives of orbital-dependent functionals is far from straightforward because of numerical difficulties and basis-set artifacts involved. In response to this challenge, we have developed a whole class of iterative methods for accurate and efficient calculation of Kohn-Sham potentials for various orbital-dependent functionals including exact exchange, hybrids, and meta-generalized gradient approximations. The presentation will overview these methods and demonstrate their dramatic advantage over existing approximations (KLI, LHF, etc.) in practical finite-basis-set calculations. [Preview Abstract] |
Tuesday, March 4, 2014 12:03PM - 12:15PM |
G1.00003: Rationalization of Hubbard U in CeOx from first principles: Unveiling the role of local structure in screening Deyu Lu, Ping Liu DFT+U method has been widely employed in theoretical studies on various ceria systems to correct the delocalization bias in local and semi-local DFT functionals with moderate computational cost. To rationalize the Hubbard U of Ce 4f, we employed the first principles linear response method to compute Hubbard U for Ce in ceria clusters, bulks, and surfaces. We found that in contrast to the commonly used approach treating U as a constant, the Hubbard U varies in a wide range from 4.1 eV to 6.7 eV, and exhibits a strong correlation with the Ce coordination numbers and Ce-O bond lengths, rather than the Ce 4f valence state. The variation of the Hubbard U can be explained by the changes in the strength of local screening due to O $\rightarrow$ Ce intersite transition. Our study represents a systematic, quantitative investigation of the relationship between the Hubbard U and the local atomic arrangement, enabling a DFT+environment-dependent U scheme that can have potential impact on catalysis research of strongly correlated systems. [Preview Abstract] |
Tuesday, March 4, 2014 12:15PM - 12:27PM |
G1.00004: Adiabatic Connection and Virial Theorem for Ensemble Density Functional Theory Aurora Pribram-Jones, Zeng-hui Yang, Carsten Ullrich, Richard Needs, Kieron Burke Ensemble density functional theory (DFT) establishes a natural framework for thermal DFT and provides excited state information inaccessible through other DFT methods. However, development of better exchange-correlation approximations is needed for this theory to be of practical use [1]. In this talk, the adiabatic connection [2] and virial theorem for ensemble DFT will be presented. In particular, their relation to exact ensemble DFT calculations, dependence on ensemble weights, and a new method for extracting exact ensemble exchange-correlation potentials will be explored. [1] Gidopoulos, N. I. and Papaconstantinou, P. G. and Gross, E. K. U. {\it Phys. Rev. Lett.}, {\bf 88}, 033003 (2002). [2] Nagy, A. {\it Int. J. Quant. Chem.}, {\bf 56}, 225 -- 228 (1995). [Preview Abstract] |
Tuesday, March 4, 2014 12:27PM - 1:03PM |
G1.00005: Hybrid Density Functionals Tuned towards Fulfillment of Fundamental DFT Conditions Invited Speaker: Matthias Scheffler Hybrid exchange-correlation functionals (XC), e.g. PBE0 and HSE, have significantly improved the theoretical description of molecules and solids. Their degree of exact-exchange admixture ($\alpha )$ is in principle a functional of the electron density, but the functional form is not known. In this talk, I will discuss \textit{fundamental conditions} of exact density-functional theory (DFT) that enable us to find the optimal choice of $\alpha $ for ground-state calculations. In particular, I will discuss the fact that the highest occupied Kohn-Sham level of an $N$-electron system ($\varepsilon _{\mathrm{HOMO}}(N))$ should be constant for fractional particle numbers between $N$ and \textit{N-1 }[1,2] and equals the ionization potential (IP) [3, 4], as given by the total-energy difference. In practice, we realize this in three different ways. XC($\alpha )$ will be optimized (opt-XC) until it $(i)$ fulfills the condition: $\varepsilon_{\mathrm{HOMO}}(N) = \varepsilon _{\mathrm{HOMO}}$(\textit{N-1/2}) or the Kohn-Sham HOMO agrees with the ionization potential computed in a more sophisticated approach $\varepsilon _{\mathrm{HOMO}}(N) =$ IP such as \textit{(ii)} the $G_{\mathrm{0}}W_{\mathrm{0}}$@opt-XC method [5,6] or \textit{(iii)} CCSD(T) or full CI [6]. Using such an opt-XC is essential for describing electron transfer between (organic) molecules, as exemplified by the TTF/TCNQ dimer [5]. It also yields vertical ionization energies of the G2 test set of quantum chemistry with a mean absolute percentage error of only $\approx $3{\%}. Furthermore, our approach removes the starting-point uncertainty of \textit{GW} calculations [5] and thus bears some resemblance to the consistent starting point scheme [7] and quasiparticle self-consistent \textit{GW} [8]. While our opt-XC approach yields large $\alpha $ values for small molecules in the gas phase [5], we find that $\alpha $ needs to be 0.25 or less for organic molecules adsorbed on metals [9]. \\[4pt] [1] J. P. Perdew et al., PRL 1982.\\[0pt] [2] P. Mori-Sanchez et al., JCP 2006.\\[0pt] [3] M. Levy et al., PRA 1984.\\[0pt] [4] T. Stein et al., PRL 2010.\\[0pt] [5] V. Atalla et al., PRB 2013.\\[0pt] [6] N. A. Richter, et al., PRL 2013.\\[0pt] [7] T. K\"{o}rzd\"{o}rfer, N. Marom, PRB 2012.\\[0pt] [8] M. van Schilfgaarde et al., PRL 2006.\\[0pt] [9] O. T. Hofmann et al., NJP 2013. [Preview Abstract] |
Tuesday, March 4, 2014 1:03PM - 1:15PM |
G1.00006: Performance of optimally-tuned range-separated hybrid functionals in predicting molecular valence-electron spectra David A. Egger, Shira Weissman, Sivan Refaely-Abramson, Sahar Sharifzadeh, Matthias Dauth, Roi Baer, Stephan Kuemmel, Jeffrey B. Neaton, Egbert Zojer, Leeor Kronik Density functional theory with optimally-tuned range-separated hybrid (OT-RSH) functionals has been recently suggested [Phys. Rev. Lett. 109, 226405 (2012)] as a non-empirical approach to accurately predict the outer-valence electronic structure of molecules. Here, we provide a quantitative evaluation of the OT-RSH approach by examining its performance in predicting the outer-valence electron spectra of prototypical gas-phase aromatic rings. For a range of up to several eV, we find that the obtained outer-valence electronic structure agrees very well (typically within 0.1-0.2 eV) with both experimental photoemission and theoretical GW data. The sole exception found is a high-symmetry orbital that is particular to aromatic rings and occurs relatively deep inside the valence state manifold. We conclude that OT-RSH functionals offer a balanced description of differently localized electronic states, a feature we find to prevail also for the more complex terpyrimidinethiol. [Preview Abstract] |
Tuesday, March 4, 2014 1:15PM - 1:27PM |
G1.00007: Electronic structure of CuPc from an optimally-tuned range-separated hybrid functional Shira Weissman, Sivan Refaely-Abramson, David A. Egger, Egbert Zojer, Leeor Kronik The optimally-tuned range separated hybrid (RSH) functional approach [1] was recently shown to allow for the calculation of the outer valence electronic spectrum of different molecules [2], resulting in good agreement with both experiment and many-body perturbation theory. The functional is based on a separation of short-range and long-range exchange components, where the range-separation parameters is tuned based on satisfaction of physical constraints, notably the ionization potential theorem. Here, we apply this approach to copper phthalocyanine (CuPc), which is of much recent interest owing to its ability to form a highly stable organic semiconductor. CuPc offers a difficult challenge for the method, because it is an open shell molecule whose electronic structure involves strongly localized $d$ orbitals. We find that the spectrum obtained for CuPc using the optimally-tuned RSH functional is in very good agreement with both experiment and MBPT calculations throughout most of the outer valence range. [1] L.Kronik, T.Stein, S.Refaely-Abramson, R.Baer,\textit{J. Chem. Theo. Comp.} (Perspectives Article) \textbf{8}, 1515 (2012). [2] S.Refaely-Abramson, S.Sharifzadeh, N.Govind, J.Autschbach, J.B.Neaton, R.Baer, L.Kronik, \textit{Phys. Rev. Lett.} \textbf{109}, 226405 (2012) [Preview Abstract] |
Tuesday, March 4, 2014 1:27PM - 1:39PM |
G1.00008: Kinetic and Hole Contributions to the Exact TDDFT Correlation Potential Kai Luo, Johanna Fuks, Ernesto Sandoval, Peter Elliott, Neepa Maitra The recent report[1-2] that dynamical steps generically develop in the exact correlation potential of time-dependent density functional theory (TDDFT) triggers the present work on the investigation on correlation potential and its adiabatic approximation. We hope this understanding will be of use in the construction of new non-adiabatic functionals capable of modeling non-linear electron dynamics using time-resolved TDDFT. We decompose the exact correlation potential into kinetic and hole contributions, analogously to what was done in the ground-state some years ago (e.g.[3]). In the ground-state, it was found that the dominant contribution was typically from the correlation hole potential, except in cases of strong correlation, when the system is far from single Slater determinant. However, this is not true in the time-dependent case: the dynamical step feature is independent of the deviation from a single-Slater determinant. Instead, the steps appear to be correlated with local oscillations of time-dependent natural orbital occupation numbers and further understanding of this connection is part of on-going investigations. [1] Elliott, Phys. Rev. Lett. 109,266404(2012) [2] Fuks, J. Phys. Chem. Lett. 4, 735(2013) [3] Gritsenko, J. Chem. Phys. 104, 8535-8545(1996) [Preview Abstract] |
Tuesday, March 4, 2014 1:39PM - 1:51PM |
G1.00009: First-Principles Studies of the Excited States and Optical Properties of Xanthene Derivative Chromophores Samia Hamed, Sahar Sharifzadeh, Jeffrey Neaton Elucidation of the energy transfer mechanism in natural photosynthetic systems remains an exciting challenge. In particular, biomimetic protein-pigment complexes provide a unique study space in which individual parameters are adjusted and the impact of those changes captured. Here, we compute the excited state properties of a group of xanthene-derivative chromophores to be employed in the construction of new biomimetic light harvesting frameworks. Excitation energies, transition dipoles, and natural transition orbitals for the low-lying singlet and triplet states of these experimentally-relevant chromophores are obtained from first-principles density functional theory. The performance of several exchange-correlation functionals, including an optimally-tuned range-separated hybrid, are evaluated and compared with many body perturbation theory and experiment. Finally, we will discuss the implication of our results for the bottom-up design of new chromophores. [Preview Abstract] |
Tuesday, March 4, 2014 1:51PM - 2:03PM |
G1.00010: Exact Factorization of the Electron-Nuclear Wavefunction: Exact Electronic Potentials in Coupled Electron-Ion Dynamics Yasumitsu Suzuki, Ali Abedi, Neepa T. Maitra, Koichi Yamashita, E.K.U. Gross We develop a novel approach to the coupled motion of electrons and ions that focuses on the dynamics of the electronic subsystem. Usually the description of electron dynamics involves an electronic Schr\"{o}dinger equation where the nuclear degrees of freedom appear as parameters or as classical trajectories. Here we derive the exact Schr\"{o}dinger equation for the subsystem of electrons, staying within a full quantum treatment of the nuclei. This exact Schr\"{o}dinger equation features a time-dependent potential energy surface for electrons (e-TDPES). We demonstrate that this exact e-TDPES differs significantly from the electrostatic potential produced by classical or quantum nuclei. \\[4pt] [1] Y. Suzuki, A. Abedi, N. T. Maitra, K. Yamashita and E. K. U. Gross, e-print arXiv:1311.3218v1 [Preview Abstract] |
Tuesday, March 4, 2014 2:03PM - 2:15PM |
G1.00011: ABSTRACT WITHDRAWN |
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