Luo Jiangshan

Sputtering pressure influence on growth morphology, surface roughness, and electrical resistivity for strong anisotropy beryllium film

The strong anisotropy beryllium (Be) films are fabricated at different sputtering pressures by direct current magnetron sputtering. With the increase of pressure, the deposition rate of Be film first increases, and when the pressure exceeds 0.8 Pa, it gradually descends. The X-ray diffraction analysis indicates that Be film is of α-Be phase, its surface always reveals the (101) crystal plane possessing the low surface energy. As for the growth morphology of Be film, the surface is mainly characterized by the fibrous grains, while the cross section shows a transition from a columnar grain to a mixed grain consisting of a cone-shaped grain and a columnar grain as the sputtering pressure increases. The large grain fraction decays exponentially from 75.0% to 59.3% with the increase of sputtering pressure p, which can improve the grain size uniformity. The surface roughness increases due to the insufficient atom diffusion, which is comparable to its decrease due to the etching effect at p 0.8 Pa, and this increase is dominated by the atom diffusion. The electrical resistivity values of Be films range from 1.7 μΩm to 2.7 μΩm in the range 0.4 Pa–1.2 Pa, which is 50 times larger than the bulk resistivity.

Static dipole polarizabilities of Scn (n ≤ 15) clusters

The static dipole polarizabilities of scandium clusters with up to 15 atoms are determined by using the numerically finite field method in the framework of density functional theory. The electronic effects on the polarizabilities are investigated for the scandium clusters. We examine a large highest occupied molecular orbital — the lowest occupied molecular orbital (HOMO–LUMO) gap of a scandium cluster usually corresponds to a large dipole moment. The static polarizability per atom decreases slowly and exhibits local minimum with increasing cluster size. The polarizability anisotropy and the ratio of mean static polarizability to the HOMO–LUMO gap can also reflect the cluster stability. The polarizability of the scandium cluster is partially related to the HOMO–LUMO gap and is also dependent on geometrical characteristics. A strong correlation between the polarizability and ionization energy is observed.

Preparation of Ag2Al intermetallic compound nanoparticles by flow-levitation method

Ag2Al intermetallic compound nanoparticles were synthesized by the flow-levitation method. The morphologies, granularity and phase structure were investigated by transmission electron microscope, X-ray diffractometer, and energy dispersive spectrometer. The results indicate that the prepared nanoparticles are regular spheres, with the grain size ranging from 20 to 110 nm. The nanoparticles are mainly composed of Ag2Al, including a little Al. The data of chemistry elementary analysis indicate that the atomic ratio of Ag to Al in the nanoparticles is about 66.5∶33.5. The grain size of Ag2Al in the prepared nanoparticles is about 33 nm, and that of Al is about 21 nm.

Study of Ni 4 PrB electronic structure and magnetism

Considering the Coulomb potential and the exchange action, electronic structure, band structure and magnetic properties of the compound Ni 4 PrB within the local spin-density approximation (LSDA) and the LSDA+ U approximation are studied through numerical simulation. The simulation results show that this system is a metallic semi-conductor and has Pr-Ni ferromagnetic coupling. The added Coulomb U effect can strongly affect magnetic properties and stable structure, and the total magnetic moment is provided by the local Ni magnetic moment before adding U effect, when the U effect is added to the system, the total magnetic moment is provided by the local Pr magnetic moment, and the system has a high structure stability. So U effect affects strongly the strong correlation, then it can describe reasonably the strong correlation and the exclusion effect caused by the spin exclusion.

Simulation of Methane Adsorption in AFS Molecular Sieves

The adsorption of methane in AFS molecular sieves was investigated by a grand canonical Monte Carlo (GCMC) simulation. The results were compared with the methane adsorption in IRMOF鄄6 materials obtained by D俟ren et al. (Langmuir, 2004, 20: 2683). It was indicated that the adsorbed amouts in AFS were very striking. AFS molecular sieve is relative ideal adsorbent in the adsorbs storage natural gas system at the medium and low pressure. The Dubinin鄄Astakhov (DA) method was employed to analyze the physical factors that affect the storage of methane.