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Tuesday, May 12, 2009
1:00 PM - 2:00 PM
CNLS Conference Room (TA-3, Bldg 1690)

Seminar

Diminished gradient dependence of density functionals: GGA`s for solids and meta-GGA`s for ordinary matter

Adrienn Ruzsinszky
Tulane University

At the generalized gradient (GGA) level of approximation, one faces the dilemma of choosing between good results for atoms and molecules or for solids. A recent PBEsol study [1] suggests that better bond lengths and lattice constants can be found when the exchange functional recovers the second-order gradient expansion over a wide range of densities. PBEsol diminishes the gradient dependence of the PBE-GGA [2], and consequently loses accuracy for the atomization energies of molecules. Better lattice constants and atomization energies are found only at the meta-GGA level of approximations. The TPSS 2003 meta-GGA [3], however, is not accurate enough for the lattice constants. This main deficiency of the TPSS semilocal functional is rectified by a better meta-GGA. With some change in the original TPSS functional suggested by the PBEsol insight, while retaining the paradigms of quantum chemistry (one ľand two- electron atoms) and solid state physics (slowly varying densities), our revised TPSS meta-GGA [4] yields very good lattice constants, surface energies, and atomization energies. This meta-GGA can be used as an ingredient of higher-level functionals like hyper-GGA`s and long-range corrected hybrids. On the other hand, for atoms and molecules, a strongly diminished PBE works well when combined with a scaled-down self-interaction correction [5] (although perhaps not significantly better than LSDA). This shows that the undiminished gradient dependence of PBE and related functionals works somewhat like a scaled-down self-interaction correction to LSDA. [1] J.P. Perdew, A. Ruzsinszky, G.I. Csonka, L.A. Constantin, X. Zhou, O.A. Vydrov, G.E. Scuseria, and K. Burke, Phys. Rev. Lett. 100, 136406 (2008). [2] J. P. Perdew, K. Burke, and M. Ernzerhof, Phys. Rev. Lett. 77, 3865 (1996) [3] J. Tao, J.P. Perdew, V.N. Staroverov, and G.E. Scuseria, Phys. Rev. Lett. 91, 146401 (2003). [4] J.P. Perdew, A. Ruzsinszky, G.I. Csonka, L.A. Constantin, and J. Sun, submitted. [5] O. A. Vydrov, G. E. Scuseria, A. Ruzsinszky, J. P. Perdew, and G. I. Csonka, J. Chem.Phys. 124, 094108 (2006).

Dr. Ruzsinszky will visit Los Alamos from 5/10 to 5/15 (before 10:am). If you would like to talk with her, please contact Dr. Jianmin Tao at jtao@lanl.gov or 667-6840.

Host: Jianmin Tao, T-4