We have studied the surfaces of zirconia (ZrO2) by first-principles calculations using density functional theory. We predict surface energies and relaxations for the principal surfaces of different bulk phases of zirconia. We find that the stoichiometric tetragonal~111! and monoclinic~1̄11! are the most stable surfaces. We find a strong linear correlation between surface energies before and afte...

Monoclinic raspite PbWO4 nanobelts were synthesized by a facile composite-salt-mediated method. By in situ heating to above 538 C inside the chamber of a transmission electron microscope, the raspite nanobelts transformed irreversibly to tetragonal scheelite phase. By analyzing the experimental data, three possible topotactic transformation relationships between raspite and scheelite phases hav...

The microscopic mechanism leading to stabilization of cubic and tetragonal forms of zirconia (ZrO2) is analyzed by means of a self-consistent tight-binding model. Using this model, energies and structures of zirconia containing different vacancy concentrations are calculated, equivalent in concentration to the charge compensating vacancies associated with dissolved yttria (Y2O3) in the tetragon...

NaFe2As2 is investigated experimentally using powder x-ray diffraction and Raman spectroscopy at pressures up to 23 GPa at room temperature and using ab-initio calculations. The results reveal a pressure-induced structural modification at 4 GPa from the starting tetragonal to a collapsed tetragonal phase. We determined the changes in interatomic distances under pressure that allowed us to conne...

Superstructure orthorhombicII (OII) phase in polycrystalline samples of YBCOx was observed by using synchrotron in-situ high resolution powder diffraction (HRPD) techniques at 300˚C. Rietveld method (RM) refinement was employed to analyse the collected diffraction data under proper oxygen partial pressure atmospheres. Our study indicates that by oxygen uptake, the samples undergo structural pha...

A reversible switching of the easy axis of magnetization for Ni on Cu(001) from in plane to out of plane is found by changing the partial pressure of hydrogen in the gas phase around the sample, allowing even for oscillations of the magnetization direction. A quantitative low-energy electron diffraction study of the diffracted intensity versus electron energy [I(E)] shows that the hydrogen-indu...

We are interested in the phase transformation from austenite to martensite. This transformation is typically accompanied by the generation and growth of small inclusions of martensite. We consider a model from geometrically linear elasticity with sharp energy penalization for phase boundaries. Focusing on a cubic-to-tetragonal phase transformation, we show that the minimal energy for an inclusi...

We are interested in the energetic cost of a martensitic inclusion of volume V in austenite for the cubic-to-tetragonal phase transformation. In contrast with the work of [Knüpfer, Kohn, Otto: Comm. Pure Appl. Math. 66 (2013), no. 6, 867–904], we consider domain with a corner and obtain a better scaling law for the minimal energy (Emin ∼ min(V , V )). Our predictions are in a good agreement wit...

Hafnia (HfO2) is a technologically important hard material with a relatively high dielectric constant and wide band gap [1]. However, the basic properties of HfO2 have been little studied in the literature due to its close resemblance to zirconia in chemical properties. In the bulk, the monoclinic (space group: P21/c) phase represents the thermodynamic minimum; phase transformation to a distort...