Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session W19: Invited Session: Frontiers of Electronic Structure Theory for Materials |
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Sponsoring Units: DCOMP Chair: Volker Blum, Duke University Room: Mission Room 103B |
Thursday, March 5, 2015 2:30PM - 3:06PM |
W19.00001: Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations and the Particle-Particle Random Phase Approximation Invited Speaker: Weitao Yang We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations, opening new a channel for density functional approximations. This resulting method has many highly desirable properties. It has minimal delocalization error with a nearly linear energy behavior for systems with fractional charges, describes van der Waals interactions similarly and thermodynamic properties significantly better than the conventional RPA, and eliminates static correlation error for single bond systems. It is the first known functional with closed-form dependence on orbitals, which captures the energy derivative discontinuity in strongly correlated systems. We also adopted pp-RPA to approximate the pairing matrix fluctuation and then determine excitation energies by the differences of two-electron addition/removal energies. This approach captures many types of interesting excitations: single and double excitations are described accurately, Rydberg excitations are in good agreement with experimental data and CT excitations display correct 1/R dependence. [Preview Abstract] |
Thursday, March 5, 2015 3:06PM - 3:42PM |
W19.00002: Towards a unified description of ground and excited state properties: \textit{GW} vs RPA and beyond Invited Speaker: Patrick Rinke In the quest for finding an ``optimal'' first principles electronic structure method, that combines accuracy and tractability with transferability across different chemical environments and dimensionalities (e.g. molecules, wires/tubes, surfaces, solids), the treatment of exchange and correlation in terms of ``exact-exchange plus correlation in the random-phase approximation (EX+cRPA)'' offers a promising avenue. Likewise one can express the same level of theory in the Green's function context through the $GW$ approximation, which has the additional advantage that quasiparticle spectra as measured by direct and inverse photoemission become accessible. In this talk I will contrast both approaches and present the latest results from our continuous assessment. We find that self-consistent (sc) $GW$ provides excellent charge densities [1], which is particularly important for charge transfer systems [2]. Spectral properties for closed shell molecules are generally in good agreement with photoemission spectra, although a judicial choice of the starting point in perturbative $G_0W_0$ calculations can outperform scGW [1,3]. Other ground state properties do not improve over EX+cRPA calculations [1]. EX+cRPA, on the other hand, provides a good description of the ground state [4] even for challenging cases like chemical reaction barrier heights [5] and the $f$-electron metal cerium [6]. The notorious underbinding of EX+cRPA can be corrected by going beyond RPA to renormalised second order perturbation theory (rPT2) [7] that gives the overall most balanced performance. I will also discuss the associated rPT2 self-energy that goes beyond $GW$.\\[4pt] [1] F. Caruso, P. Rinke, X. Ren, M. Scheffler, and A. Rubio, Phys. Rev. B {\bf 86}, 081102(R) (2012), {\it ibid} Phys. Rev. B {\bf 88}, 075105 (2013).\\[0pt] [2] F. Caruso, V. Atalla, A. Rubio, M. Scheffler, and P. Rinke, Phys. Rev. B {\bf 90}, 085141 (2014).\\[0pt] [3] N. Marom, F. Caruso, X. Ren, O. Hofmann, T. K\"orzd\"orfer, J. R. Chelikowsky, A. Rubio, M. Scheffler, and P. Rinke, Phys. Rev. B {\bf 86}, 245127 (2012).\\[0pt] [4] X. Ren, P. Rinke, C. Joas, and M. Scheffler, J. Mat. Sci. {\bf 47}, 7447 (2012).\\[0pt] [5] J. Paier, X. Ren, P. Rinke, G. E. Scuseria, A. Gr\"uneis, G. Kresse, and M. Scheffler, New J.\ Phys.\ {\bf 14}, 043002 (2012).\\[0pt] [6] M. Casadei, X. Ren, P. Rinke, A. Rubio, and M. Scheffler, Phys. Rev. Lett. \textbf{109}, 14642 (2012).\\[0pt] [7] X. Ren, P. Rinke, G. E. Scuseria, and M. Scheffler, Phys. Rev. B {\bf 88}, 035120 (2013) [Preview Abstract] |
Thursday, March 5, 2015 3:42PM - 4:18PM |
W19.00003: Range-separated Hybrid Functionals for Molecules and Interfaces Invited Speaker: Thomas K\"orzd\"orfer Density functional theory (DFT) and its time-dependent extension (TD-DFT) are powerful tools enabling the theoretical prediction of the ground- and excited-state properties of many-electron systems with reasonable accuracy at affordable computational costs. The DFT treatment of particular electronic and structural properties, however, reveals severe qualitative failures of standard out-of-the-box functionals. Important examples include the wrong level alignment and spurious charge-transfer at organic-organic interfaces as well as the underestimation of bond-length alternations and excited-state energies in polymers. These failures can be traced back to the delocalization error inherent to semilocal and global hybrid functionals. In this talk, I will discuss recent efforts to reduce the delocalization error by using range-separated hybrid functionals combined with a non-empirical tuning procedure for the range-separation parameter [1-3]. The benefits and drawbacks of using range-separated hybrid functionals for the description of the ground and excited states of molecules and interfaces will be discussed. It will be demonstrated that this approach provides for robust and efficient means of calculating ionization potentials and electron affinities, for characterizing the electronic couplings in organic mixed-valence systems, for the calculation level alignment at organic/organic interfaces, and for the reliable prediction of the optical band-gap of low band-gap polymers. I will further motivate why RSH functionals provide for a superior starting point for non-self-consistent {\it GW} calculations as compared to standard semilocal or global hybrid functionals. \\[4pt] [1] T. K\"orzd\"orfer and J.-L. Br\'edas, Acc. Chem. Res. {\bf 47}, 3284 (2014). \newline [2] C. Sutton, T. K\"orzd\"orfer, M. Gray, M. Brunsfeld, R. Parrish, C. D. Sherrill, J. S. Sears, and J.-L. Br\'edas, J. Chem. Phys. {\bf 140}, 054310 (2014). \newline [3] T. K\"orzd\"orfer, R. M. Parrish, J. S. Sears, C. D. Sherrill, and J.-L. Br\'edas, J. Chem. Phys. {\bf 137}, 124305 (2012). [Preview Abstract] |
Thursday, March 5, 2015 4:18PM - 4:54PM |
W19.00004: New Developments in Diffusion QMC for materials Invited Speaker: Fernando Reboredo |
Thursday, March 5, 2015 4:54PM - 5:30PM |
W19.00005: Stochastic Quantum Chemistry for extended systems Invited Speaker: George Booth |
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