942 research outputs found
Ferroelectricity in ultra-thin perovskite films
We report studies of ferroelectricity in ultra-thin perovskite films with
realistic electrodes. The results reveal stable ferroelectric states in thin
films less than 10 \AA thick with polarization normal to the surface. Under
short-circuit boundary conditions, the screening effect of realistic electrodes
and the influence of real metal/oxide interfaces on thin film polarization are
investigated. Our studies indicate that metallic screening from the electrodes
is affected by the difference in work functions at oxide surfaces. We
demonstrate this effect in ferroelectric PbTiO and BaTiO films.Comment: 4 pages in REVTEX4, 4 epsf figure
A More Accurate Generalized Gradient Approximation for Solids
We present a new nonempirical density functional generalized gradient
approximation (GGA) that gives significant improvements for lattice constants,
crystal structures, and metal surface energies over the most popular
Perdew-Burke-Ernzerhof (PBE) GGA. The new functional is based on a diffuse
radial cutoff for the exchange-hole in real space, and the analytic gradient
expansion of the exchange energy for small gradients. There are no adjustable
parameters, the constraining conditions of PBE are maintained, and the
functional is easily implemented in existing codes.Comment: 5 pages, corrected the errors of the sublimation energy of Ih ic
- …