Formation condition of solid solution type high-entropy alloy

Formation condition of high-entropy alloys with solid solution structure was investigated. Seventeen kinds of the high-entropy alloys with different components were prepared, the influencing factors （the comprehensive atomic radius difference δ, the mixing enthalpy AH and the mixing entropy AS） of phase composition of the alloys were calculated, and the microstructure and phase compositions of alloys were analyzed by using SEM and XRD. The result shows that only the systems with δ≤2.77 and △H≥-8.8 kJ/mol will form high entropy alloy with simple solid solution. Otherwise, intermetallic compounds will exist in the alloys. So, selection of the type of element has important effects on microstructure and properties of high entropy alloys.

影响酸强度的结构因子探讨

影响酸强度的结构有多种因素，本文分析探讨了各种因素对酸电离过程的作用机理。

Roles of heteroatoms in electrocatalysts for alkaline water splitting:A review focusing on the reaction mechanism

Alkaline water splitting is a promising technology for“green hydrogen”generation.To improve its efficiency,highly robust catalysts are required to reduce the overpotential for low electrical power consumption.Heteroatom modification is one of the most effective strategies for boosting catalytic performance,as it can regulate the physicochemical properties of host catalysts to improve their intrinsic activity.Herein,aiming to provide an overview of the impact of heteroatoms on catalytic activity at the atomic level,we present a review of the key role of heteroatoms in enhancing reaction kinetics based on the reaction pathways of the hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)in alkaline media.In particular,the introduction of heteroatoms can directly and indirectly optimize the interactions between the active sites and intermediates,thus improving the intrinsic activity.To clearly illustrate this influence in detail,we have summarized a series of representative heteroatom-modified electrocatalysts and discussed the important roles of heteroatoms in the OER and HER reaction pathways.Finally,some challenges and perspectives for heteroatom-modified electrodes are discussed.We hope that this review will be helpful for the development of efficient and low-cost electrocatalysts for water electrolysis and other energy conversion applications.

Hooke's Atom in an Arbitrary External Electric Field: Analytical Solutions of Two-Electron Problem by Path Integral Approach

By using the path integral approach, we investigate the problem of Hooke＇s atom （two electrons interacting with Coulomb potential in an external harmonic-oscillator potential） in an arbitrary time-dependent electric field. For a certain infinite set of discrete oscillator frequencies, we obtain the analytical solutions. The ground state polarization of the atom is then calculated. The same result is also obtained through linear response theory.

Shape Coexistence and Band Termination in Doubly Magic Nucleus ^40Ca

Shape coexistence and band structure near yrast line of the Z ＝ N doubly magic nucleus 40Ca have been investigated by the configuration-dependent cranked Nilsson-Strutinsky approach. The observed normal deformed and superdeformed bands are explained and the terminating states are confirmed by the calculations. The transition quadrupole moment Qt of the calculated superdeformed band is in good agreement with the observed one at high spin. There is shape coexistence within the same configuration. Possible normal deformed and superdeformed bands with rotation around the intermediate axis in several interesting configurations of40Ca are discussed. Possible favored superdeformed band terminations in 38Ca and 38Ar are predicted. The experimental results in 38Ar are discussed simply.

Emerging dual-atomic-site catalysts for electrocatalytic CO_(2)reduction

The electrochemical CO_(2)reduction reaction(CO_(2)RR)to yield high-value added fuels and chemicals provides a promising approach towards global carbon neutrality.Constant endeavors have been devoted to the exploration of high-efficiency catalyst with rapid reaction kinetics,low energy input,and high selectivity.In addition to the maximum metal atomic utilization and unique catalytic performance of single-atom catalyst(SAC),dual-atomic-site catalysts(DASCs)offer more sophisticated and tunable atomic structure through the modulations of another adjacent metal atom,which can bring new opportunities for CO_(2)RR as a deeper extension of SACs and have recently aroused surging interest.In this review,we highlight the recent advances on DASCs for enhancing CO_(2)RR.First,the classification,synthesis,and identification of DASCs are provided according to the geometric structure and electronic configuration of dual-atomic active sites.Then,the catalytic applications of DASCs in CO_(2)RR are categorized based on marriage-type,hetero-nuclear,and homo-nuclear dual-atomic sites.Particularly,the structure-activity relationship of DASCs in CO_(2)RR is elaborately summarized through systematically analyzing the reaction pathways and the atom structures.Finally,the opportunities and challenges are proposed for inspiring the design of future DASCs with high structural accuracy and high CO_(2)RR activity and selectivity.

Lead-free perovskites: growth, properties, and applications

Lead halide perovskites have attracted extensive attention in recent years because of their excellent photoelectronic properties, such as high absorption coefficients,carrier mobilities, defect tolerances, and photoluminescence efficiencies. However, a key issue hindering their commercial application is the toxicity of lead. Replacing lead with other nontoxic elements is a promising solution to this problem.Considering their atomic radii, relative atomic masses, and electron arrangements, perovskites based on Sn, Bi, Sb, and other elements instead of Pb have been widely synthesized.Here, we summarized the growth methods, photoelectric properties, and device applications of these lead-free perovskites. First, we introduced several common growth methods for lead-free perovskites, including solution methods,solid-state reaction, and chemical vapor deposition methods.Second, we discussed the photoelectric properties and methods for optimizing these properties of lead-free perovskites with different structure dimensions. Finally, the applications of lead-free perovskites in solar cells, light-emitting diodes,and X-ray detectors were examined. This review also provides suggestions for future research on lead-free perovskites.

Radial breathing modes of multi-walled carbon nanotubes by an atomic beam-spring model

Based on molecular force fields,a new finite element model is constructed for multi-walled carbon nanotubes where the interlayer interactions and C--C bonds are simulated by the elements of piece-wise linear spring and rectangular cross section beam,respectively.For high computation efficiency and atomic reification,the radial breathing modes of multi-walled carbon nanotubes are studied systemically using this model.The results show the correspondence between carbon nanotube structures and vibrational modes,which provide unequivocal data for the experimental characterization of carbon nanotubes.An empirical relationship of radial breathing modes frequencies with the nanotube radius are also obtained for two-layer carbon nanotubes.

Predicting macroscopic thermal expansion of metastable liquid metals with only one thousand atoms

Results of thermal expansion prediction from atomic scale for metastable liquid metals are reported herein. Three pure liquid metals Ni, Fe, and Cu together with ternary Ni60Fe20Cu20 alloy are used as models. The pair distribution functions were em- ployed to monitor the atomic structure. This indicates that the simulated systems are ordered in atomic short range and disor- dered in long range. The thermal expansion coefficient was computed as functions of temperature and atom cutoff radius, which tends to maintain a constant when the cutoff radius increases to approximately 15A. In such a case, slightly more than 1000 atoms are required for liquid Ni, Cu, Fe and Ni60Fe20Cu20 alloy, that is, the macroscopic thermal expansion can be pre- dicted from the volume change of such a tiny cell. Furthermore, the expansion behaviors of the three types of atoms in liquid Ni60Fe20Cu20 alloy are revealed by the calculated partial expansion coefficient. This provides a fundamental method to predict the macroscopic thermal expansion from the atomic scale for liquid alloys, especially in the undercooled regime.

Microbial Reduction of Graphene Oxide by Shewanella

Graphene oxide （GO） can be reduced to graphene in a normal aerobic setup under ambient conditions as mediated by microbial respiration of Shewanella cells. The microbially-reduced graphene （MRG） exhibited excellent electrochemical properties. Extracellular electron transfer pathways at the cell/GO interface were systematically investigated, suggesting both direct electron transfer and electron mediators are involved in the GO reduction.

First principles study on methane reforming over Ni/TiO2（110） surface in solid oxide fuel cells under dry and wet atmospheres

Understanding the carbon-tolerant mechanisms from a microscopic view is of special importance to develop proper anodes for solid oxide fuel cells.In this work,we employed density-functional theory calculations to study the CH4 reaction mechanism over a Ni/TiO2 nanostructure,which experimentally demonstrated good carbon tolerance.Six potential pathways for methane reforming reactions were studied over the Ni/TiO2(110)surface under both dry and wet atmospheres,and the main concerns were focused on the impact of TiO2 and Ni/TiO2 interface on CO/H2 formation.Our calculations suggest that the reaction between carbon and the interfacial lattice oxygen to form CO*is the dominant pathway for CH4 reforming under both dry and wet atmospheres,and intervention of steam directly to oxidize C*with its dissociated OH*group is less favorable in energy than that to wipe off oxygen vacancy to get ready for next C*oxidation.In all investigated paths,desorption of CO*is one of the most difficult steps.Fortunately,CO*desorption can be greatly promoted by the large heat released from the previous CO*formation process under wet atmosphere.H2O adsorption and dissociation over the TiO2 surface are found to be much easier than those over Ni,yttria stabilized zirconia(YSZ)and CeO2,which should be the key reason for the greatly depressed carbon deposition over Ni-TiO2 particles than traditional YSZ-Ni and CeO2-Ni anode.Our study presents the detailed CO*formation mechanism in CH4 reforming process over the Ni/TiO2 surface,which will benefit future research for exploring new carbon-tolerant solid oxide fuel cell anodes.

Influence of filling atoms on radial collapse and elasticity of carbon nanotubes under hydrostatic pressure

Using molecular mechanics and molecular dynamics simulations, we focus on the influence of filling atoms on radial collapse and elasticity of single-walled carbon nanotubes(SWNTs). It is shown that the filled argon(Ar) and silicon(Si) atoms can effectively improve the resistance to high pressure and radial elasticity of SWNT, which may attribute to the strong repulsive force from the filled Ar(Si) atoms. However, due to the strong interaction of Cu atoms, filling Cu atoms deteriorate SWNT's radial elasticity. In addition, it is found that the phase transitions of the atoms filled in SWNT occur in the process of loading and unloading pressure, so that the electrical properties of the SWNTs filled with atoms change in the process of loading and unloading pressure. In view of the restorability of SWNT filled with Si atoms upon unloading, the filled SWNTs can be used to develop a new class of nano-electronic devices such as pressure sensor, relay and memory, etc.