Defect structure of β-LiAl

Simultaneous viscosity and density measurements and modeling of 2-alcohols at temperatures between (291 and 353) K and pressures up to 50 MPa

The dilation of the α-Fe lattice by manganese (0 to 2.4 at.%) has been determined by lattice parameter and density measurements at 25°C. The results may be described within experimental error by the linear expressions Q = QFe−0.0071 × (at.% Mn) g.cm−3 (density measurement) and a0 = aFe + 0.00067 × (at.% Mn) Å (X-ray measurement). The virtual absence of dilation at Mn contents below 0.6at.%, reported in two previous investigations, is suggested as having resulted from internal oxidation of Mn.

Lattice parameter and density data were compiled for Y 2 O 3 ‐Stabilized ZrO 2 , both from the literature and from experimental measurements. The data are described very well over a wide range of composition by the model of Aleksandrov et al. , which assumes Y substitution for Zr in the unit cell with compensating anion vacancies. Effects are noted in two‐phase cubic‐tetragonal materials which indicate significant lattice strains in the two‐phase materials.

Solid solution hardening is sought and observed in two B2(cP2) CsCl and two C15(cF24) Cu2Mg type structures. New data are presented for the high-temperature compounds AlCo, AlRu, and Cr2Zr; prior data of Livingston on Cu2Mg are analyzed. From lattice parameters and specific gravities, cell occupancy numbers have been measured and used to infer likely defect types and concentrations. The effects of constitutional defects in binary compounds correlate with traditional substitutional solution hardening from elastic interactions due to size differences and modulus differences. The hardening from ternary solutes is similar in magnitude, but the defect structures are complicated and not yet adequately understood.

Electronic structure of non-stoichiometric NiAl

We analysed x-ray powder diffraction data of spray pyrolytic precursor powders for the oxide-powder-in-tube (OPIT) technology by means of the Rietveld method. For calcinations in air we find a typical phase composition of 2212, 14-24, 11, CP and 3321 at 800 °C (13 h). At 820 °C 2212 is in equilibrium with 14-24 and CP after 48 h calcination. In 8% O2 at 800 °C 2212 exists together with 14-24, 21, CP and CuO, in 99.999% N2 at 760 °C the stable phase assemblage consists of 2212, 21 and CuO. The highest amount of 2212 can be found in the powder calcined at 8% O2 (72.4 wt%) compared with 68.9 wt% for the powder calcined in 21% O2 and 69.3 wt% for the powder calcined in flowing N2. A first trace of 2223 can be observed in powders calcined in air at temperatures of 838 °C and 842 °C. The crystallographic features of the 2212 phase correlate with the calcination atmosphere: under reducing atmospheres the satellite reflections of the x-ray powder diffractogram disappear and the orthorhombic lattice distortion z increases due to Pb2+-incorporation into 2212. With increasing O-content the c lattice parameter becomes significantly shorter in samples calcined in oxidizing atmospheres. It is possible to infer a cationic ratio of Sr:(Sr + Ca) ≈ 0.12 for the 11 phase and Ca:(Ca + Sr + Bi) ≈ 0.57 for 14-24 in precursors from lattice parameter data.

The aggregation behavior of trimetazidine hydrochloride in aqueous solutions at different temperatures

Use of precision density and lattice parameter measurements for study of point defects in single crystals of semiconductors: II. Determination of homogeneity regions of compounds, the Vegard law application

Experimental data of densities, viscosities, and refractive indices of {(benzyl alcohol + methanol), ethanol, 1-propanol, 2-propanol, 1-butanol, and 2-butanol} binary mixtures were measured at T = 298.15 K and ambient pressure (81 500 Pa) using an oscillating densimeter, Ubbelohde capillary viscometer, and digital Abbe refractometer, respectively. Values of excess molar volumes, VmE, of the binary mixtures in the liquid phase at T = 298.15 K have been derived from density measurements. The experimental data are used to calculate partial molar volumes, Vi, excess partial molar volumes, ViE, excess partial molar volumes at infinite dilution, ViE,∞, deviations in the viscosity, Δη, and deviations in the refractive index, ΔnD, excess refractive index, nDE, and kinematic viscosity, ν. The calculated quantities VmE, Δη, ΔnD, and nDE have been correlated with the Redlich–Kister equation. The excess partial molar volumes, ViE,∞, and enthalpies, HiE,∞, at infinite dilution of the binary mixtures were computed by a...

La-doped $\mathrm{BaSn}{\mathrm{O}}_{3}$ films were grown on $\mathrm{DySc}{\mathrm{O}}_{3}$ substrates by molecular beam epitaxy using La, Ba, and $\mathrm{Sn}{\mathrm{O}}_{2}$ sources with and without additional oxidant, respectively. Lattice parameter measurements as a function of growth conditions show a reduced lattice parameter that is likely due to substitution of $\mathrm{S}{\mathrm{n}}^{2+}$ on the Ba site. The propensity for the antisite defect is discussed as being due to the combination of oxygen-poor, Sn-rich conditions and the dual valence of Sn. Although electron mobilities are highest for films with reduced lattice parameters, antisite defects will pose an upper limit to thin film mobility. Less Sn-rich conditions lead to the formation of another defect that causes a lattice expansion. The combined effects of these defects on the lattice parameter can compensate each other and cause the appearance of a stoichiometric lattice parameter for nonstoichiometric films with poor electrical behavior.

Half-metallic ferromagnets like the full Heusler compounds with formula X$_2$YZ are supposed to show an integer value of the spin magnetic moment. Calculations reveal in certain cases of X = Co based compounds non-integer values, in contrast to experiments. In order to explain deviations of the magnetic moment calculated for such compounds, the dependency of the electronic structure on the lattice parameter was studied theoretically. In local density approximation (LDA), the minimum total energy of Co$_2$FeSi is found for the experimental lattice parameter, but the calculated magnetic moment is about 12% too low. Half-metallic ferromagnetism and a magnetic moment equal to the experimental value of $6\mu_B$ are found, however, only after increasing the lattice parameter by more than 6%. To overcome this discrepancy, the LDA$+U$ scheme was used to respect on-site electron correlation in the calculations. Those calculations revealed for Co$_2$FeSi that an effective Coulomb-exchange interaction $U_{eff}=U-J$ in the range of about 2eV to 5eV leads to half-metallic ferromagnetism and the measured, integer magnetic moment at the measured lattice parameter. Finally, it is shown in the case of Co$_2$MnSi that correlation may also serve to destroy the half-metallic behavior if it becomes too strong (for Co$_2$MnSi above 2eV and for Co$_2$FeSi above 5eV). These findings indicate that on-site correlation may play an important role in the description of Heusler compounds with localized moments.

3 - Vacancy and defect structures in metal oxides

This work introduced the high-throughput phase prediction of PtPd-based high-entropy alloys via the algorithm based on a combined Korringa-Kohn-Rostoker coherent potential approximation (KKR-CPA) and artificial neural network (ANN) technique. As the first step, the KKR-CPA was employed to generate 2,720 data of formation energy and lattice parameters in the framework of the first-principles density functional theory. Following the data generation, 15 features were selected and verified for all HEA systems in each phase (FCC and BCC) via ANN. The algorithm exhibited high accuracy for all four prediction models on 36,556 data from 9139 HEA systems with 137,085 features, verified by R2 closed to unity and the mean relative error (MRE) within 5%. From this dataset comprising 5002 and 4137 systems of FCC and BCC phases, it can be realized based on the highest tendency of HEA phase formation that (1) Sc, Co, Cu, Zn, Y, Ru, Cd, Os, Ir, Hg, Al, Si, P, As, and Tl favor FCC phase, (2) Hf, Ga, In, Sn, Pb, and Bi favor BCC phase, and (3) Ti, V, Cr, Mn, Fe, Ni, Zr, Nb, Mo, Tc, Rh, Ag, Ta, W, Re, Au, Ge, and Sb can be found in both FCC and BCC phases with comparable tendency, where all predictions are in good agreement with the data from the literature. Thus, the combination of KKR-CPA and ANN can reduce the computational cost for the screening of PtPd-based HEA and accurately predict the structure, i.e., FCC, BCC, etc.

Lattice parameter and defect structure of cadmium oxide containing foreign atoms

In our work, the model of self-consistent electron–deformation–diffusion effects in thin films grown on substrate with the mismatch of lattice parameters of the contacting materials is constructed. The proposed theory self-consistently takes into account the interaction of the elastic field (created by the mismatch of lattice parameters of the film and the substrate, and point defects) with the diffusion processes of point defects and the electron subsystem of semiconductor film. Within the framework of the developed model, the spatial distribution of deformation, concentration of defects, conduction electrons and electric field intensity is investigated, depending on the value of the mismatch, the type of defects, the average concentrations of point defects and conduction electrons. It is established that the coordinate dependence of deformation and the concentration profile of defects of the type of stretching (compression) centers, along the axis of growth of the strained film, have a non-monotonic character with minima (maxima), the positions of which are determined by the average concentration of point defects. It is shown that due to the electron–deformation interaction in film with a lattice parameter mismatch, the spatial redistribution of conduction electrons is observed and n-n+ transitions can occur. Information about the self-consistent spatial redistribution of point defects, electrons and deformation of the crystal lattice in semiconductor materials is necessary for understanding the problems of their stability and degradation of nano-optoelectronic devices operating under conditions of intense irradiation.