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# Search results

40 records were found.

## Tunability of High-Dielectric-Constant Materials from First Principles

Comment: 6 pages, MRS Spring 2002 proceedings

## Ferroelectricity in PbTiO3 thin films: A first principles approach

The ground-state ferroelectric distortion of PbTiO3 thin films is studied using a first-principles effective Hamiltonian to describe the structural energetics at a microscopic level. Under short-circuit electrical and zero-stress mechanical boundary conditions, (0 0 1) films as thin as one unit cell are found to support a stable perpendicular polarization. Size effects in the layer-by-layer ferroelectric distortion are discussed. The continuum limit of the first-principles effective Hamiltonian has the same form as the widely-used Landau-Ginzburg expression for the free energy near T-c, so that the present results can be directly related to those of previous phenomenological studies. In particular, a microscopic interpretation of the extrapolation length delta is proposed.

## Epitaxially strained [001]-(PbTiO$_3$)$_1$(PbZrO$_3$)$_1$ superlattice and PbTiO$_3$ from first principles

Comment: 8 pages, 5 figures

## Coexistence of antiferrodistortive and ferroelectric distortions at the PbTiO$_3$ (001) surface

The c(2$\times$2) reconstruction of (001) PbTiO$_3$ surfaces is studied by means of first principles calculations for paraelectric (non-polar) and ferroelectric ([001] polarized) films. Analysis of the atomic displacements in the near-surface region shows how the surface modifies the antiferrodistortive (AFD) instability and its interaction with ferroelectric (FE) distortions. The effect of the surface is found to be termination dependent. The AFD instability is suppressed at the TiO$_2$ termination while it is strongly enhanced, relative to the bulk, at the PbO termination resulting in a c(2x2) surface reconstruction which is in excellent agreement with experiments. We find that, in contrast to bulk PbTiO$_3$, in-plane ferroelectricity at the PbO termination does not suppress the AFD instability. The AFD and the in-plane FE distorti...

## Fcc breathing instability in BaBiO_3 from first principles

Comment: submitted to PRB, completely revised version after referee report

## A Microscopic Model of Ferroelectricity in Stress-free PbTiO3 Ultrathin Films

Comment: 4 pages, 1 figure (revised version)

## Band gap and stability in the ternary intermetallic compounds NiSnM (M = Ti, Zr, Hf): A first principles study

Comment: 27 pages (Sections IVB, IVE rewritten; PRB April 15 II 1995 issue)

## Polymorphism and metastability in NbN: Structural predictions from first principles

Comment: 11 pages, in RevTex, 3 uuencoded figures

## First-principles studies of ferroelectric oxides

The application of first-principles methods to the study of ferroelectric oxides is reviewed. While the main focus is on the perovskites, particularly the most-studied compounds BaTiO3, PbTiO3, and SrTiO3, other oxide families, including LiNbO3, layered perovskites, nitrites and nitrates, and electronic and magnetic ferroelectrics, are included. Results are presented for crystal structure, polarization and dielectric and piezoelectric coefficients. The identification of lattice instabilities through the computation of phonon dispersion relations for a high-symmetry reference phase is presented. Results at nonzero temperature, obtained through effective Hamiltonian and interatomic potential approaches, are given. Calculations for solid solutions, defects, thin films, superlattices and nanostructures are described. Challenges and prospec...

## Lattice instabilities of PbZrO3/PbTiO3 [1:1] superlattices from first principles

Comment: 12 pages, 2 figures, 7 tables, submitted to PRB