Chen Qingdong

Density Functional Theory Study of Several Nitrotriazole Derivatives

Quantum chemical calculations at B3LYP/6-31G* and B3P86/6-31G* levels are used to predict the bond dissociation energies (BDEs) of seven nitrotriazole derivatives. It is noted that the BDEs of the initial scission step are between 44 and 70 kcal/mol, which are larger than those of piperidine and diazocine compounds and polynitro benzoate molecules. In addition, substituent groups greatly affect the bond dissociation energies of the title compounds. The heats of formation (HOFs) for seven energetic materials are also calculated via designed isodesmic reactions. From computational results it is noted that substituent groups strongly affect the HOFs. The research demonstrated that the HOF of the compound substituted by a five-membered ring is larger than those substituted by a six-membered ring for 1,2,4-triazole. The detonation performance data of the title compounds are also calculated according to the HOFs calculated by B3LYP/6-31G* level.

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.