Monte Carlo simulations at constant pressure are used to characterize the structure of the restricted primitive model in the tetragonal-ordered solid phase. A method to estimate the location of the order-disorder transition and the densities of the coexistence phases is discussed. The results support the weakly first-order character of the transition.

The nanocrystalline powders and polycrystalline materials on the basis of stabilized zirconia with tetragonal type of structure have been investigated. The forms of the normal vibrations of the tZrO2 have been built using the theory group methods. The peculiarities of experimentally obtained Raman spectra of studied materials have been explained with the help of analysis of symmetry and the for...

Iron selenide obtained by mild hydrothermal reaction is not superconducting and exhibits a triclinic crystal structure below 60 K unlike superconducting FeSe from conventional solid state synthesis which is orthorhombic. In contrast, tetragonal iron sulphide FeS from hydrothermal synthesis is superconducting but undergoes no structural change on cooling.

The "hard" paraelectrics as a material with a high dielectric constant and low loss at microwave frequencies are considered. The impact of different types of polarization on the dielectric and thermal properties of paraelectric is described. The tetragonal rutile structure is considered and the influence of the oxygen octahedrons TiO6 on the dielectric constant of the paraelectric is establishe...

The newly discovered superconductor FeSe(1-x) (x approximately 0.08, T(c)(onset) approximately 13.5 K at ambient pressure rising to 27 K at 1.48 GPa) exhibits a structural phase transition from tetragonal to orthorhombic below 70 K at ambient pressure-the crystal structure in the superconducting state shows remarkable similarities to that of the REFeAsO(1-x)F(x) (RE = rare earth) superconductors.

Strontium titanate (SrTiO 3) is one of the best studied substances showing a displacive phase transition [1]. At ambient temperature, it exhibits a cubic perovskite structure with the space group Pm3m. On cooling, a Brillouin zone-boundary softmode drives the second-order transition to an antiferrodis-tortive phase at T C = 105 K. The primary order parameter is the antiphase rotation of TiO 6-o...

Hydrides of Nd2Ni2In were synthesized. Nd2Ni2In crystallizes in the tetragonal Mo2FeB2 structure type. Hydrogen absorption changes the crystal structure to orthorhombic (space group Pbma) so as to accommodate a higher amount of hydrogen. The unit-cell volume increases by 15.5 % for Nd2Ni2InH4.5 and by 21.6 % for Nd2Ni2InH6. Hydrogenation emphasizes antiferromagnetic coupling, but the Néel tempe...

We have calculated the electronic structure of the tetragonal L10 ordered FeCu by solving self-consistently a tight-binding Hamiltonian for s, p and d electrons. We have found by total energy calculation that this structure is ferromagnetic. In addition, we have determined that the equilibrium ratio between the interlayer and the intralayer lattice parameters is 0.947. PACS numbers: 75.50.Rr, 7...

Using DFT methods we have studied structure, equation of state, and phase behavior of BaTiO3. We have identified the pressure induced phase transformations from the rhombohedral to orthorhombic structure at ca. 5 GPa and from tetragonal phase to cubic phase at ca. 7.5 GPa. INTRODUCTION BaTiO3 is an important example perovskite structured ceramic displaying ferroelectric property. At high temper...

Powder neutron diffraction has been used to study the nature of the structural transition away from the Fd3m cubic structure upon cooling below ∼285 K in the spinel LiMn2O4. We report powder data taken between 10 K and 333 K and propose a large cell tetragonal structure in space group I41/amd for the material at 100 K. While complete segregation of the Mn3+ and Mn4+ ions is not possible in this...