HR: 09:15h
AN: V21A-06    [PDF]
TI: New Non-local Density Functionals for More Accurate First-principles Calculations
AU: * Wu, Z
EM: z.wu@gl.ciw.edu
AF: Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Rd., N.W, Washington, DC 20015
AU: Cohen, R E
AF: Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Rd., N.W, Washington, DC 20015
AU: Singh, D J
AF: code 6391, Naval research Lab, Washington, DC 20375
AB: Although the density functional theory based on local density approximation (LDA) and (general gradient approximation) GGA are extraordinarily successful, they fail to predict certain properties accurately. The weighted density approximation (WDA), which incorporates nonlocal information through a model exchange-correlation (xc) hole, was proposed to fix the drawbacks of LDA and GGA. We used a uniform xc G function to calculate ground-state properties of some common perovskite ferroelectric materials. The WDA yields much better equilibrium volumes than LDA for the cubic structure. The WDA also gives correct description of ferroelectric instability. However, For the relaxed structure of tetragonal PbTiO\$\_3\$, WDA predicts a strain and volume bigger than experiment. We also presented WDA for rare-earth trihydrites, YH\$\_3\$ and LaH\$\_3\$. The LDA predicts YH\$\_3\$ and LaH\$\_3\$ as semi-metals. We investigate some commonly used pair-distribution functions G. These calculations show that the WDA can predict a substantial insulating gap while at the same time retaining structural properties in accord with experimental data. Our WDA band structures agree with those of \$GW\$ approximation very well, but the calculated band gaps are still 1.0-2.0 eV smaller than experimental findings. This work is Supported by ONR.
DE: 3200 MATHEMATICAL GEOPHYSICS (New field)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting