Li Liben

Theoretical investigation on crystal structure, detonation performance and thermal stability of a high density cage hexanitrohexaazaisowurtzitane derivative

AbstractDensity functional theory calculations were performed to study the new polynitro cage compound with the similar framework of HNIW. IR spectrum, heat of formation and thermodynamic properties were predicted. The bond dissociation energies and bond orders for the weakest bonds were analysed to investigate the thermal stability of the title compound. The detonation and pressure were evaluated by using the Kamlet–Jacobs equations based on the theoretical density and condensed HOFs. In addition, the results show that there exists an essentially linear relationship between the WBIs of N–NO2 bonds and the charges –QNO2 on the nitro groups. The crystal structure obtained by molecular mechanics belongs to P21/C space group, with lattice parameters Z = 4, a = 12.3421 Å, b = 24.6849 Å, c = 20.4912 Å, ρ = 1.896 g cm − 3. The designed compound has high thermal stability and good detonation properties and is a promising high energy density compound. Graphical AbstractThe IR spectrum, heat of formation and thermodynamic properties of a new polynitro cage compound were calculated by theoretical method. The results show that the obtained crystal structure belongs to P21/C space group. There exists a good linear relationship between the WBIs of N-NO2 bonds and the charges –QNO2.

Effect of Annealing Temperature on the Structural and Electrical Properties of a-Axis-Oriented SrTiO3 Films

Strontium titanate films with high a-axis-orientation [a(100) = 94.1%] were deposited on (111) Pt/Ti/SiO2/Si substrates by the metal organic deposition process. X-ray diffraction shows that the degree of a-axis orientation increases with increasing annealing temperature. It is found that the dielectric properties are improved by a higher annealing temperature, while the leakage currents are also enhanced, and the possible causes of temperature dependence are discussed.

Gradient-stress on polarization in Ba1-xSrxTiO3 films

A group of position-thickness-dependent stresses are used to modified Landau-Devonshire theory to investigate the second-order phase transition in Ba1−xSrxTiO3 films. The result shows that the short-range interaction between the unit cells of the film and the substrate induces the phase transition dispersion and the rise of the transition temperature in the films. The dependence of the effective dielectric constant on the temperature and the average spontaneous polarization on the film thickness are computed, which qualitatively agree with the experiments.