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Numerous theoretical simulation works have predicted the fantastic properties of arsenene, such as a tunable band gap, topological states, and a high carrier mobility. However, the experimental syn...

The mechanism of tandem dimethylamine-borane (NHMe2BH3, DMAB) dehydrogenation and alkene hydrogenation catalyzed by [Pd(NHC)(PMe3)] are investigated by density functional theory (DFT) calculations [NHC = N,N′-bis(2,6-diisopropylphenyl) imidazole-2-ylidene]. Four possible DMAB dehydrogenation mechanisms have been carefully investigated involving concerted B H/N H activation, sequential B H/N H activation, sequential N H/B H activation, and proton transfer mechanism. DFT studies show that the N H proton transfers to ligated carbene carbon and sequential C H/B H activation is the most kinetically favorable pathway with the lowest activation barrier of 23.8 kcal/mol. For hydrogenation, it was found that a trans-dihydride Pd(II) complex, [Pd(H)2(NHC)(PMe3)], formed in the dehydrogenation process, serves as an effective catalyst for reduction of trans-stilbene.

We use a two-dimensional electrostatic model to explore Van der Pauw (VdP) method on samples with holes. Results of electrostatic simulation based on the model are consistent with the experimental results. The quantitative investigation of VdP method on sample with one hole indicate the value of f, i.e. the right hand side of VdP equation, is depend on the position of contacts and the size of holes. We also quantitatively explore the VdP method used on sample with two holes in special position of contacts and sample geometry. According to the guidance of simulation and experiment, we find proper position of contacts, which make VdP equation f = 1 valid again on sample with holes. It is helpful for the optimization of VdP method and measuring the resistivity of sample with holes.

A quantum-chemical mechanistic investigation using density functional theory (DFT) on ammonia-borane dehydrogenation catalyzed by a series of iron bis(phosphinite) pincer complexes is reported. A metal-ligand cooperation mechanism has been proposed, in which the hydrogen atom of B H moves to metal Fe and proton of N H transfers to pincer ipso carbon simultaneously with the lowest activation barriers. DFT calculations and natural bond orbital (NBO) charge analysis suggest that Fe POCOP complex with an electron-donating MeO group at the para position to the ipso carbon exhibits the highest catalytic activity. A plausible explanation of the observed catalytic activities is also given.

The recent process in the fabrication of the ordered Ge/Si quantum dots (QDs) is reviewed. The fabrication step generally started on the preparation of patterned substrate prepared in advance by using several interesting methods, such as photo lithography, focus ion beam (FIB), reactive ion etching (RIE), and extreme ultraviolet lithography (EUV-IL) et al, which are introduced briefly in this article. Here, we’d like to focus on the detailed process of nanosphere lithography (NSL) which has the advantages of less cost and higher product compared with the referred methods. The ordered Ge nanostructures always show as Hexagonal close-packed array on the patterned Si substrate and have the advantages of potential applications in electronic and optoelectronic devices.

Possible mechanisms of copper-catalyzed N–H/C–H activation from N-phenylbenzamidine to 2-phenylbenzimidazole have been investigated using density functional theory (DFT) calculations. In comparison with the C–H activation mechanism, the N–H/C–H activation with a Cu-assisted concerted metalation–deprotonation (CMD) mechanism is found to be more kinetically favorable. Facile occurrence of the studied reactions is supported by the low activation energies of their respective rate-determining steps. A possible alternative mechanism involving a Cu–H agostic transition state is presented, but it is unfavored by the relatively higher activation barriers.

The catalytic dehydrogenation of ammonia borane (NH 3 BH 3 ) with the Ir pincer complex, [Ir(I t Bu′) 2 ] + , has been investigated by density functional theory (DFT). A mechanism has been proposed for dehydrogenation process involving three possible pathways: stepwise B–H/N–H activation, concerted B–H/N–H activation and proton transfer mechanism. The facile occurrence of the studied systems was demonstrated by the activation barriers of the rate-determining steps. It was found that the proton transfer pathway is mostly kinetically favorable with the lowest activation barrier of 28.38 kcal/mol.

Nitrogen (N)-doped zinc oxide (ZnO) particles were successfully synthesised by a simple and economical ammonia-assisted hydrothermal method. The samples were characterised by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and ultraviolet–vis diffuse reflectance. It was found that N-doped ZnO exhibited higher photocatalytic activity than commercial Degussa P25 towards the liquid-phase degradation of Rhodamine B and methylene blue under simulation of solar light. The authors attribute these results to enhanced visible-light absorption ability and efficient separation of photogenerated carriers. The authors hope that this study provides valuable information on the design of specific ZnO photocatalytic materials for further industrial application.

The ultraviolet optical transition of the isomeric state in 229Th has attracted much attention recently due to its potential application to building an atomic/nuclear clock with ultra-high precision. However, the lowest nuclear excitation energy and the lifetime of the first excited state of 229Th were not measured directly and precisely until now, and how to precisely determine this isomer state of the 229Th is an urgent requirement. Here an experimental approach of using a technique similar to that of dielectronic recombination to measure the transition energy of the isomer state of 229Th at heavy ion storage rings is described. It is expected that the resonant transition can be found and determined with a precision better than several milli-eV.

We reconsider the bipolaronic system by introducing the squeezed-polaron model or two-phonon coherent state, and obtain more satisfactory results than before with respect to lowering the system's ground-state energy and extending the singlet superconducting phase in the phase diagram of such a bipolaronic system. The necessity and the limit of using our variational treatment to this bipolaronic system are also discussed.

The dynamics of electron tunneling between double quantum dots is investigated t heoretically in terms of a perturbation method based on a unitary transformation . Considering electron coupling with phonons, the dynamical tunneling current is obtained analytically. The phonon-induced decoherence is studied in detail. A possible decoupling mechanism is proposed.

Via a reconsideration of a simple model for bipolarons we have shown that in order to keep the total energy of the model system being a stable minimum a new phonon coherent state should be introduced as a result of the electron-phonon interaction. Thus it could be infered that the reduction effect of phonons is much weaker and the range of the singlet bipolaronic state as the stable ground state configuration is more extensive that what the previous authors considered.

Via discussions of the simple model of a strong electron-phonon interacting system, the authors develop a new variational treatment for dealing with the superconducting properties of such a system. The key idea of their treatment is to introduce a two-phonon coherent state for the phonon subsystem so that the ground-state energy of the interacting system can arrive at a stable minimum. They have shown that the superconducting condensation energy in their variational state is of a reasonable magnitude and that the effective mass of the polarons is much smaller than that considered by previous researchers. The gap equation and the expression for critical temperature Tc in the theory are also different from those in ordinary polaronic state as well as from those in Bardeen-Cooper-Schrieffer theory. The authors have pointed out the possibility of high-Tc superconductivity in such an interacting system.

The ground-state properties of the Sm-based mixed valence compounds are discussed by means of introducing an indirect on-site hybridization mediated by phonons, for the direct on-site hybridization is forbidden by inversion symmetry. A self-consistent field approximation is used, and a nonzero energy gap and a fluctuating valence state are given. The results obtained can be used to explain the small energy gap and the valence fluctuation phenomena observed in SmB6 and SmS.

The electron-phonon interactions in valence fluctuation systems have been reconsidered and a new procedure has been developed to transform the author's model Hamiltonian, which is a periodic Anderson model with indirect hybridisation, by a unitary transformation of the displacement operator type. Then, a variational ground state of the phonons subsystem has been constructed; thus the electron and the phonon subsystems could be separated approximately and an effective Hamiltonian for the electron subsystem could be obtained. Finally, a functional integration approach has been used to investigate the ground-state properties of the effective Hamiltonian, and the ground-state phase diagrams have been given. By requiring that the total ground-state energy of the model system should be a minimum, he has found that the ground state of the phonon subsystem must be a two-phonon coherent state which is different from any eigenstate of phonon number operators. Also, the author has shown that through the electron-phonon interaction the f-f Hubbard U-term could contribute to the d-f hybridisation and he considers that this contribution might be used to explain why most of valence fluctuation systems have a strongly correlated f band but are not in any magnetic state.

A new variational ground state of a system with strong electron-phonon interaction has been proposed in which the electron subsystem is in a superconducting pairing state and the phonon subsystem is in a two-phonon coherent state. We have shown that such a variational state is necessary for obtaining reasonable magnitudes for the superconducting condensation energy and for the effective mass of the charge carriers.

We have investigated the ground-state properties of a model system with a strong electron-phonon interaction. It is found that as long as the renormalized intersite electron correlation is attractive, a new type of Cooper pairing will occur whether the renormalized on-site electron correlation is repulsive or attractive. Furthermore, we have shown that a new phonon coherent state, named a two-phonon coherent state, must be introduced to serve as the ground state of the phonon subsystem, so that the ground-state energy of the interacting system can be made a stable minimum and an appropriate condensation energy of the superconducting ground state may be obtained. We have performed numerical calculations for the n = 1 case.

In this paper, a new variational ground state of strong electron-phonon interacting system is proposed, in which the electron subsystem is in superconducting pairing state and the phonon subsystem in two -phonon coherent state. We show that such a variational state is necessary for obtaining a superconducting condensation energy with reasonable magnitude and for the effective mass of the charge carriers not being too large.

Two-magnon Raman spectra of RbNiF3 are calculated for the temperature range between 0 K to Néel point TN(= 133 K). From considerations of the general symmetry principle and the experimental results, we have derived the Hamiltonian of interaction between the magnetic system and the radiation field. The method of the equation of motion of retarded Green's function is used to obtain the analytic expression of the two-magnon Raman scattering intensity. In the two-magnon propagator, both the effects of energy renormalization and the life time have been taken into account. Finally, quantitative calculations are performed with proper approximations using computer. Although there are no adjustable parameters, the results account very well for the observed temperature dependence of both the. peak position and the line width in the range from 0 K up to TN.

This article deals with the exciton-phonon interaction which has important effects on the properties of the charge transfer excitons (CTE) in alkali halide crystals. An interaction mechanism: the modulation of the Hamiltonian of the CTE system by the vibrations of the constituent ions, which may play an important role, is studied. The CTE-phonon interaction Hamiltonian is derived. From this interaction Hamiltonian, we have discussed the lifetime of the CTE. The linewidths calculated self-consistently under proper approximations agree semiquantitatively with the data measured by experiments in the literature. So we consider that this interaction Hamiltonian may present the important exciton-phonon interaction in alkali halide crystals.

Via a reconsideration of a simple model for bipolarons, we have shown that in order to-keep the total energy of the model system to be a stable minimum, a new phonon coherent state should be introduced as a result of the electron-phonon interaction. Thus it could be in-fered that the reduction effect of phonons is much weaker and the range of the singlet bipo-laronic state as the stable ground state configuration is more extensive than what the previous authors considered.