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Center for Nonlinear Studies |
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 –and 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