Bulletin of the American Physical Society
2008 APS March Meeting
Volume 53, Number 2
Monday–Friday, March 10–14, 2008; New Orleans, Louisiana
Session Q13: Ground State Density Functional Theory: Applications |
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Sponsoring Units: DCOMP Chair: Kieron Burke, University of California, Irvine Room: Morial Convention Center 204 |
Wednesday, March 12, 2008 11:15AM - 11:27AM |
Q13.00001: Polarizabilities and Hyperpolarizabilities of Hydrogen Chains: Is Self-Interaction Correction the Key? A. Ruzsinszky, J.P. Perdew, G.I. Csonka, G.E. Scuseria, O.A. Vydrov Semi-local density functionals like the local spin density and generalized gradient approximations are known to overestimate [1, 2] the polarizabilities and especially the hyperpolarizabilities of long-chain molecules, while these quantities are much better predicted by exact-exchange methods (Hartree-Fock or Optimized Effective Potential). The source of this failure of the semilocal approaches for the electric response is rooted in the self-interaction error inherent to the semilocal approximations. We show here that the semi-local functionals, after full or scaled-down Perdew-Zunger self-interaction correction [3, 4], are even better than the exact-exchange methods for these quantities. \newline [1] S. K\"{u}mmel, L. Kronik, J. P. Perdew, Phys. Rev. Lett. \textbf{93,} 213002 (2004). \newline [2] C. D. Pemmaraju, S. Sanvito, K. Burke, arXiv:0708.2814v1. \newline [3] J. P. Perdew, A. Zunger, Phys. Rev. B. \textbf{23}, 5048 (1981). \newline [4] O. A. Vydrov, G. E. Scuseria, A. Ruzsinszky, J. P. Perdew, G. I. Csonka, J. Chem. Phys. \textbf{124}, 094108 (2006). [Preview Abstract] |
Wednesday, March 12, 2008 11:27AM - 11:39AM |
Q13.00002: Improved Description of Stereoelectronic Effects Using Semi-local Density Functional Theory Gabor I. Csonka, John P. Perdew, Adrienn Ruzsinszky Proper description of stereoelectronic (SE) effects is desirable for any theoretical method to be used in organic chemistry. The SE design rules are frequently used in synthetic organic chemistry to design and explain new reactions by electron donating and withdrawing effects or steric interactions. These effects are often poorly described by standard generalized gradient approximations for exchange and correlation. Many popular exchange-correlation functionals are biased toward the correct description of free atoms and fail to improve upon LSDA for solids. Changing two parameters within the PBE form to satisfy different constraints leads to a new non-empirical GGA, PBEsol [1], that performs well for solids and improves the description of large organic systems and reactions. We present examples where this new non-empirical functional provides considerable improvements for molecules. [1] J.P. Perdew, A. Ruzsinszky, G.I. Csonka, O.A. Vydrov, G.E. Scuseria, L.A. Constantin, X. Zhou, and K. Burke, http://arxiv.org/abs/0711.0156 [Preview Abstract] |
Wednesday, March 12, 2008 11:39AM - 11:51AM |
Q13.00003: Approximations in local hybrid density functionals Benjamin Janesko, Gustavo Scuseria Hybrid density functionals incorporating a fraction of exact (Hartree-Fock-type) electronic exchange have become one of the dominant approximations for modeling the electronic structure of large molecules and solids. Generalization to a position dependent admixture of exact exchange provides a route to improved accuracy. However, such local hybrid functionals generally have a significant computational expense. We present work towards approximate density functionals that incorporate some of the desirable properties of local hybrids, without requiring explicit evaluation of exact exchange. These results show promise for extending the benefits of hybrid functionals to larger systems. [Preview Abstract] |
Wednesday, March 12, 2008 11:51AM - 12:03PM |
Q13.00004: The role of middle-range Hartree-Fock-type exchange in hybrid functionals Thomas Henderson, Artur Izmaylov, Gustavo Scuseria, Andreas Savin While hybrid functionals are responsible for many successes in modern Kohn-Sham theory, they have several drawbacks. The slow decay of nonlocal exchange makes hybrids computationally demanding in extended systems with small bandgaps, while in finite systems the rapid decay of semilocal exchange causes errors in quantities sensitive to the long-range potential. Both problems can be addressed by range-separated hybrids which include nonlocal exchange only for some values of the interelectronic separation. Excluding long-range nonlocal exchange in extended systems improves computational efficiency without loss of accuracy, while including full long-range nonlocal exchange in finite systems improves accuracy without loss of efficiency. Both approaches use a significant fraction of nonlocal exchange for intermediate electronic separations. We show that a hybrid functional that uses nonlocal exchange only for this middle range has many advantages, properly describing thermochemistry, reaction barriers, and bandgaps in the same framework. [Preview Abstract] |
Wednesday, March 12, 2008 12:03PM - 12:15PM |
Q13.00005: Molecular Crystals, a test system for weak bonding. Bernard Delley, Teodora Todorova Intermolecular binding in molecular crystals are due to electrostatic and Van-der-Waals interactions. Crystal parameters are crucially dependent on the accuracy of the electronic model. We investigate sets of molecular crystals, classified by the lowest non-vanishing molecular multipole moment, with density functional theory. We find that certain density functional approximations give an almost surprisingly good description of such lattices, deteriorating only moderately going from molecules with dipole moment, to ones with quadrupole and to even higher symmetry molecules, where finally Van- der-Waals interactions dominate at large distance. For the best performing density functional approximations, even the VdW subset has an error range of calculated lattice parameters comparable to crystals with covalent, ionic or metallic bonds. [Preview Abstract] |
Wednesday, March 12, 2008 12:15PM - 12:27PM |
Q13.00006: Surface Stress and Energy of Metal Nanoclusters Igor Vasiliev, Bharat Medasani, Young Ho Park We combine first-principles and empirical computational methods to study the surface energy and surface stress of silver and aluminum nanoparticles. The structures, cohesive energies, and lattice contractions of Ag and Al nanoclusters over a broad size range are analyzed using two theoretical approaches: an {\it ab initio} density functional pseudopotential technique combined with the generalized gradient approximation and the embedded atom method. Our calculations predict the surface energy of Ag and Al nanoclusters to be in the region of 1.0$-$2.2 J/m$^2$ and 0.9$-$2.0 J/m$^2$, respectively. The surface stress is evaluated from the average lattice contraction by considering the hydrostatic pressure on the surface of a spherical particle. A comparison of the calculated surface energies and stresses indicates a greater degree of surface reconstruction in Al nanoclusters than in Ag nanoclusters. [Preview Abstract] |
Wednesday, March 12, 2008 12:27PM - 12:39PM |
Q13.00007: Applying Density Functional Theory for Atomic Vacancies in Solids Xiaolan Zhou, John P. Perdew We use a new generalized gradient approximation of density functional theory -- PBEsol, a revised Perdew-Burke-Ernzerhof GGA, to calculate the vacancy formation energies and other properties of metals and semiconductors: Al, Pt, Pd, GaN [1], etc. By restoring the gradient expansion over a wide range of density gradients, PBEsol [2] yields excellent jellium exchange and correlation surface energies. We expect that this new functional will improve the description of vacancies in real materials, since the vacancy formation energy is essentially the work needed to create an interior surface. \newline [1] Thomas R.Mattsson and Ann E. Mattson. Phys. Rev. B \textbf{66}, 214410 (2002). \newline [2] John P. Perdew, Adrienn Ruzsinszky, Gabor I. Csonka, Oleg A. Vydrov, Gustavo E. Scuseria, Lucian A. Constantin, Xiaolan Zhou, and Kieron Burke, Restoring the density-gradient expansion for exchange in solids and surfaces, http://arxiv.org/abs/0711.0156 [Preview Abstract] |
Wednesday, March 12, 2008 12:39PM - 12:51PM |
Q13.00008: Generalized LDA$+$U$+$V functional in DFT calculations for covalent systems Vivaldo Campo, Matteo Cococcioni In this work, we introduce a generalized LDA$+$U$+$V functional that consists in both on-site (U) and inter-site (V) interactions. While V can be straightforwardly obtained from the same linear-response approach used to calculate U [1], its inclusion in the ``$+$U'' energy functional can improve the treatment of systems where electrons tend to localize on molecular states (bonds) rather than on atomic orbitals, and will extend the applicability of this approach to a much broader class of systems. Because of a better treatment of hybridization, this extension also helps avoiding well-known drawbacks of ``standard'' (atomic) LDA$+$U such as the exaggerated down-shift of the energy of localized filled orbitals. It thus results in an improved energetic description, which is crucial for studying structural relaxations, chemical reactions and phase transitions. Paradigmatic examples of application of this generalized approach will include diatomic molecules, TM oxides and group-IV solids. $^1$ M. Cococcioni and S. de Gironcoli, Phys. Rev. B {\bf 71}, 035105 (2005). [Preview Abstract] |
Wednesday, March 12, 2008 12:51PM - 1:03PM |
Q13.00009: Comparative Study of the Performance of DFT B3PW91 for the Prediction of Electronic Properties of Molecules Jasma Batham, Pedro Derosa Density Functional Theory is a widely used and accepted tool for the prediction of ground state molecular properties. However and despite the fact that the hybrid GGA functional B3PW91 has proven to be successful for many application, its use seems not to be as widespread. In a paper by Zhang and Musgrave the HOMO, the LUMO and the energy difference between the two (HLG), is compared for a set of 27 molecules to the experimental ionization potential (IA), electron affinity (EA), and the lowest excitation energy respectively. The first two are inspired by the Koopman's theorem that suggests that the HOMO is a good approximation of -IP while the negative of the LUMO is an approximation of the -EA. Notably, in the mentioned paper, results for 11 different DFT functional are compared but B3PW91 is not one of them. In this work we compare the performance of B3PW91, to that of B3LYP, also a hybrid functional, and the corresponding non-hybrid GGAs BLYP and BPW91 for the same 27 molecules. For all the cases the 6-311+G** basis set is used. We compare HOMO, LUMO and HLG to the experimental IP, EA, and first excitation energy among the four methods. In addition we formally calculated the IP and EA as the difference in energy between the corresponding ion and the neutral. B3PW91 show at least comparable results to other methods more commonly used. [Preview Abstract] |
Wednesday, March 12, 2008 1:03PM - 1:15PM |
Q13.00010: Relativistic Density Functional Theory Calculations of the Electron Paramagnetic Resonance Parameters for Vanadyl Acetyl Acetonate and Copper Acetyl Acetonate Laxman Mainali, Indra Sahu, Keith Earle Relativistic density functional theory calculations of electron paramagnetic resonance (EPR) parameters using a variety of basis sets have been computed for the model systems Vanadyl acetyl acetonate and Copper acetyl acetonate using the ORCA program. The basis set dependence of g and A tensor calculations for Vanadyl acetyl acetonate and Copper acetyl acetonate were studied using Pople Style and Ahlrichs basis sets in Local and gradient corrected functionals (BP86 and PWP) and Hybrid functionals (B3LYP and PW1PW). The PW1PW hybrid functional gives the best values for VO(acac)$_{2}$ using the TZV basis set and for Cu(acac)$_{2}$ using the 6-311G(d) basis set. The calculated A values with PW1PW hybrid functional for VO(acac)$_{2}$ and Local and gradient corrected functional (BP86) for Cu(acac)$_{2}$ with same basis set (DZ) give better results than previously reported values using the Amsterdam Density Functional Theory (ADF) Software. Our calculated g and A tensor values are in good agreement with the values determined from experiment. [Preview Abstract] |
Wednesday, March 12, 2008 1:15PM - 1:27PM |
Q13.00011: ABSTRACT WITHDRAWN |
Wednesday, March 12, 2008 1:27PM - 1:39PM |
Q13.00012: Functional minimization scheme for first-principles electronic structure calculations with bi-orthogonal interpolating wavelets William Garber, Dmitri Volja, Wei Ku A new development of first-principles electronic method will be presented based on direct energy functional minimization and bi-orthogonal wavelet basis set. The employment of bi- orthogonal basis allows systematically controlled accuracy while benefiting from the compact support that allows O(N) algorithms. Furthermore, utilization of the interpolating nature of the wavelet, together with the effectiveness of multi-resolution of wavelet, enables very efficient calculation without compromising accuracy. By avoiding solving eigenvalue equation as in standard Kohn-Sham framework, the method is easily extended to parallel algorithms, and allows simple implementation of various non- local functionals. In case of crystals, our method gives directly solution as Wannier functions, further utilizing their sparseness. This new development is ideal for easy implementation and accurate systematic benchmarking of various modern functionals, and holds the potential to attack very large systems such as nano- materials. [Preview Abstract] |
Wednesday, March 12, 2008 1:39PM - 1:51PM |
Q13.00013: An implementation of LDA+DMFT within the PAW framework: Application to SrVO3. Bernard Amadon, Frank Lechermann, Antoine Georges The combination of LDA and DMFT has been used in the past ten years to understand properties of strongly correlated systems. Different interfaces have been used such as Linear Muffin Tin Orbitals and Maximally Localized Wannier Functions. Such schemes are however restricted to simple systems because the construction of wannier functions is demanding or because another simplification is used (such as the atomic sphere approximation). We present a new implementation of LDA+DMFT, which keeps the precision of the Wannier implementation, but which is lighter. It relies on the projection of Kohn-Sham states over localized orbitals to define the correlated subsystem. We have implemented this method within the Projector Augmented Wave framework. This thus opens the way to electronic structure calculations within LDA+DMFT for more complex structures. We present an application to SrVO3. The results are compared to calculations done on the Wannier basis and we discuss the features of the total spectral function. [Preview Abstract] |
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