Pressure and Temperature Induced Phase Transition of ZnS from First-Principles Calculations

The pressure induced phase transition of ZnS from the wurtzite （WZ） and the zincblende （ZB） structures to the rocksalt （RS） structure and the temperature induced phase transition from the ZB structure to the WZ structure are investigated by ab initio plane-wave pseudopotential density-functional theory （DFT）, together with the quasiharmonic Debye model. It is found that the zero-temperature transition pressures from the WZ-ZnS and the ZB-ZnS to the RS-ZnS are 17.20 and 17.37 GPa, respectively. The zero-pressure transition temperature from the ZB-ZnS to the WZ-ZnS is 1199 K. All these results are consistent with the available experimental data. Moreover, the dependences of the normalized primitive cell volume V/V0 on pressure and thermal expansion coefficient α on temperature are also obtained successfully.     

Structures and Equation of State of ε-Fe under High Pressure

The equation of state （EOS） and the axial ratio c/a of ε-Fe at high pressures are investigated by using the gen- eralized gradient approximation （GGA） within the plane-wave pseudopotential density functional theory （DFT）. The results show that at the lower pressure, the EOS of ferromagnetic ε-Fe is consistent with the experimental result. While at higher pressure, the EOS of the nonmagnetic ε-Fe is in good agreement with the experimental result. Meanwhile, we find an obvious increase of the axial ratio c/a with pressure, and there is only a small increase with increasing temperature at high pressure.     

Translocation of Biopolymer Chain Through a Nanopore: Coil--Helix Transition

The translocation dynamics of a single biopolymer chain through a nanopore in a membrane is investigated by taking the coil-helix transition into account. Based on the changing of the free energy due to the coil-helix transition, the mean first passage time T is obtained, and then the corresponding numerical simulations are presented under different conditions. It is shown that the coil--helix transition can significantly shorten the translocation time of the biopolymer chain. In addition, we also discuss the scaling behaviour for T with the chain length N and some related problems.     

Deformation induced microtwins and stacking faults in aluminum single crystal

Microtwins and stacking faults in plastically deformed aluminum single crystal were successfully observed by high-resolution transmission electron microscope. The occurrence of these microtwins and stacking faults is directly related to the specially designed crystallographic orientation, because they were not observed in pure aluminum single crystal or polycrystal before. Based on the new finding above, we propose a universal dislocation-based model to judge the preference or not for the nucleation of deformation twins and stacking faults in various face-centered-cubic metals in terms of the critical stress for dislocation glide or twinning by considering the intrinsic factors, such as stacking fault energy, crystallographic orientation, and grain size. The new finding of deformation induced microtwins and stacking faults in aluminum single crystal and the proposed model should be of interest to a broad community.     

Quantum competitions between the effects of the interlayer exchange couplings and the magnetically structural symmetry in a four-layer ferrimagnetic superlattice

The magnon energy spectra, the sublayer magnetization and the quantum fluctuations in a ferrimagnetic superlattice consisting of four different magnetic sublayers are studied by employing the linear spin-wave approach and Green's function technique. The effects of the interlayer exchange couplings and the spin quantum numbers on the sublayer magnetization and the quantum fluctuations of the systems are discussed for three different spin configurations. The roles of quantum competitions among the interlayer exchange couplings and the symmetry of the different spin configurations have been understood. The magnetizations of some sublayers increase monotonously, while those of others can exhibit their maximum, and the quantum fluctuations of the whole superlattice system can show a minimum when one of the antiferromagnetic interlayer exchange couplings increases. This is due to the quantum competition/transmission of effects of the interlayer exchange couplings. When the spin quantum number of sublayers varies, the system goes through from a quantum region of small spin numbers to a classical region of large spin numbers. The quantum fluctuations of the system exhibit a maximum as a function of the spin quantum number of a sublayer, which is related with higher symmetry of the system. It belongs to the type III Shubnikov group of magnetic groups. This magnetically structural symmetry consists of not only the symmetry of space group, but also the symmetry of the direction and strength of spins.     

Exchange bias in patterned FeMn/NiFe bilayers

Electron beam lithography and ion beam etching have been used to pattern a wire-like array in FeMn/NiFe bilayers. The variation of hysteresis loops with the etching depth in FeMn layer has been presented, and it has been found that with increasing etching depth the coercivity increases and M–H loops show an asymmetric kink. Detailed studies of the magnetic behaviors of the asymmetric kink in the patterned sample with 3.5 nm thick FeMn layer have been performed, and a magnetization component perpendicular to the wire direction has been observed.     

A spectroscopic proof of a surface equilibrium between on top and bridge bonded CO at Pt(1 1 0) in acid solution

According to most of works in the literature, adsorbed carbon monoxide at Pt(1 1 0) electrodes in acid media presents only linear bonded (CO_L) so-called, atop geometry. In the present work, the formation of bridge bonded carbon monoxide (CO_B) is shown via in situ infrared FT spectra, measured on a Pt(1 1 0) electrode covered with 25% CO, in HClO₄ solutions. For the first time, the inter conversion between atop and bridge bonded CO at potentials in the hydrogen adsorption region is reported in acid solution. Band intensity and band center frequency indicate dipole–dipole coupling effects in spite of the low CO total coverage.     

硼氢化锂储氢材料研究*

车载储氢是推进氢燃料车规模化商业应用的“瓶颈”环节,开发高性能车载储氢材料/技术成为当前能源及材料领域关注的热点。近年来,随着储氢材料领域的不断拓展,以硼氢化锂（LiBH₄）为典型代表的高储量配位金属氢化物日渐成为新兴的储氢材料研究热点。本文从体系成分/反应路径调整、纳米结构调制、阴/阳离子替代及催化体系构建等方面概述了改善LiBH4综合储/放氢性能的最新研究进展,旨在明确配位硼氢化物储氢材料研究中的关键问题及可能的解决途径。     

Quantitative approach for the prediction of preferential sorption in the case of pervaporation of a physico-chemically similar binary mixture

Selective transport by pervaporation of physico-chemically similar and polar components through a polar membrane is complicated due to competitive sorption and diffusion phenomena. In the present study the mechanism of preferential sorption has been predicted for such a system, methanol-ethylene glycol-cellophane. The mechanism has been explained in terms of intercrystalline swelling of the polymer matrix in presence of increasing methanol concentration in the feed. The reduction in preferential sorption at increasing wt% of methanol in the feed may be due to the increasing accessibility of the membrane towards ethylene glycol. This phenomenon has been quantitatively explained by considering a non-linear dependence on concentration of the binary liquid-polymer interaction parameter. Theoretical sorption data have been derived from the Flory-Huggins thermodynamics by using the swelling equilibrium condition. The coupling and plasticization phenomena in sorption are explained in terms of liquid-polymer interaction parameters. The theoretical results show good agreement with previously published experimental data.