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The structural, mechanical, and electronic properties of Ni–Co-based layered transition oxide LiNixCo1−xO2 (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, and 0.9) (LNCO) have been investigated using the first-principles method. The results show that the effect of Ni/Co mixing on the structural property is slight. For the case of the mechanical property, the elastic constant, elastic modulus, such as Young’s modulus ( Y), Poisson’s ratio ( v), Pugh’s ratio ( B/ G), and Cauchy pressure ( C′) of LNCO have been carefully analyzed based on the strain-energy method. The results demonstrate that the mechanical strength of LNCO materials is weaker than that of pure LiCoO2 (LCO) and LiNiO2 (LNO). However, the B/G ratio and Poisson’s ratio of LNCO are greater than that of the pure LCO and LNO, which means that Ni/Co mixing can improve the ductility of pure LCO and LNO. In addition, Cauchy pressure and anisotropy are also discussed, and as cathode materials, LNCO still exhibits good electrical conductivity. Our results provide a feasible way to realize mechanical property modulation by Ni–Co-based layered transition metal oxides LCO. Furthermore, our study is also helpful to reveal the formation mechanism of intra-lattice microcracks in electrode materials. more...

Based on plasma kinetic theory, the instabilities of self-gravitation systems under perturbation with orbital angular momentum (OAM) are investigated, and the concept of twisted Jeans mode is introduced to describe the new phenomenon. The result shows that the growth rate of the Jeans instability is enhanced with the OAM parameter increased, while the critical wave number is consistent with the classical Jeans critical value. It is expected that the present results would give more insight into the evolution and dynamics of a self-gravitational system. more...

In the present paper, the characteristic behaviors of the sheath in an unmagnetized dusty plasma that contained trapped electrons, cold ions, and variable-charged dusts are investigated, based on the Sagdeev potential approach. The result shows that both the formation and structure of the sheath are modified by the trapped electrons. At the sheath edge, the critical ion Mach number decreases as the trapping parameter β increases. It is noted that the effect of electron trapping on the ion-entering-sheath-velocity is indirect, and closely related to the dust charge variation. In the sheath, the increased β leads to the enlargement of the sheath thickness and the absolute value of electrostatic potential, which results in the redistribution of particle densities. Moreover, the results of the Maxwellian case are essentially recovered when β = 1. As expected, the present results can give more insight into the interaction processes that happened on the plasma-wall interface. more...

We study the phase sensitivity of an SU(1,1) interferometer with photon loss by using three different photon operations schemes, i.e., performing photon-addition operation on the input port of the SU(1,1) interferometer (Scheme A), the interior of SU(1,1) interferometer (Scheme B), and both of them (Scheme C). We compare the performance of the three schemes in phase estimation by performing the same times of photon-addition operation to the mode b. The results show that Scheme B improves the phase sensitivity best in ideal case, and Scheme C performs well against internal loss, especially in the case of strong loss. All the three schemes can beat the standard quantum limit in the presence of photon loss, but Scheme B and Scheme C can break through the standard quantum limit in a larger loss range. more...

A first-principles calculation was performed to investigate the switchable CO2 capture on χ3-borophene by injecting/removing the extra electrons. The results show that the CO2 adsorption energy on the neutral χ3-borophene is 0.150 eV. After extra 2.5 e are injected, the adsorption energy is raised up to 0.802 eV, showing a significant enhancement with the change from the physical adsorption to chemical adsorption. Furthermore, both the CO2 capture and release processes are exothermic reactions involving injecting/removing extra electrons. χ3-borophene possesses a metallic electronic structure, which is conducive to the injection of extra electrons. The minimum charge density for CO2 capture on the negatively charged χ3-borophene is 1.6 × 1014 e cm-2. The CO2 capture capacity of χ3-borophene is 4.09 × 1014 cm-2. Finally, we study the selectivity of negatively charged χ3-borophene. The results show that the negatively-charged χ3-borophene possesses a high selectivity for CO2 from its mixtures with CO, CH4, NH3, N2, H2S, and H2. χ3-borophene is a new promising charge-modulated switchable CO2 capture material with good stability, high CO2 capture capacity, high selectivity, and excellent electrical conductivity. more...

The phase sensitivity of SU(1,1) interferometer is investigated using a coherent state and an m-coherent superposition squeezed vacuum states as inputs and the intensity detection. Photon-subtraction, photon-addition and photon superposition are three special cases. Both ideal and realistic cases are considered. It is shown that the coefficient s of coherent superposition can modulate the performance of phase sensitivity, especially in a small squeezing region. Even in the presence of photon losses, the three-kind of non-Gaussian operations can achieve the improvement of measure precision, and the photon addition presents the best robustness compared to the photon subtraction and coherent superposition. For small squeezing, the first-order non-Gaussian operation may be the most preferred in improving phase sensitivity if considering the limitations of experimental conditions. Our results may be helpful for the practical application of quantum information. more...

Recently, plasma CO2 hydrogenation to generate valuable products (e.g. CO and CH4, hydrocarbons and oxygenates) has attracted more and more attention. The conversion of carbon dioxide (CO2) and hydrogen (H2) in an atmospheric non-thermal plasma was investigated by a zero-dimensional plasma kinetic model. This paper focuses on the effect of different feed gas composition ratios (H2/CO2 volume ratio) on the plasma CO2 hydrogenation reaction mechanisms. It is found that H2 addition in plasma not only promotes CO2 dissociation but also changes the plasma chemistry, which seems to significantly enhance the electron density and temperature. Besides, larger H2 content in the H2/CO2 mixture is beneficial to obtaining a higher number density of methanol, which is in good agreement with published experimental data. The temporal distributions of abundant radicals, ions and molecule densities are determined under a series of initial hydrogen content. Conversions of inlet H2/CO2 and selections toward CO and CH4 are calculated and presented. The primary reaction channels related to the production and destruction of CO, H, CH2O, CH3OH, CH4 and H2O are determined. Finally, the underlying overall reaction mechanisms regarding the plasma CO2 hydrogenation are analyzed in detail by the chemical reaction flow chart. more...

The dust-induced instability involving charge fluctuations is studied in rotating dusty plasma. Due to dust charging dynamics, the dust-induced instability mode which was first put forward by Mikhailovskii et al. [A.B. Mikhailovskii, S.V. Vladimirov, J.G. Lominadze, V.S. Tsypin, A.P. Churikov, N.N. Erokhin, R.M.O. Galvao, Phys. Plasmas 15, 014504 (2008)] will be replaced by dust-charging-rotational instability (DCRI) mode. Comparing to the dust-induced instability, the new instability mode also exists in an increasing rotation frequency profile, but always with a greater growth rate. The analysis indicates that the rotational instability mode induced by dust charge is always unstable. The present results may be used to investigate the rotating dusty plasma experiments and observations. more...

A first-principles calculation was performed to investigate the switchable CO2 capture on χ3-borophene by injecting/removing the extra electrons. The results show that the CO2 adsorption energy on the neutral χ3-borophene is 0.150 eV. After extra 2.5 e are injected, the adsorption energy is raised up to 0.802 eV, showing a significant enhancement with the change from the physical adsorption to chemical adsorption. Furthermore, both the CO2 capture and release processes are exothermic reactions involving injecting/removing extra electrons. χ3-borophene possesses a metallic electronic structure, which is conducive to the injection of extra electrons. The minimum charge density for CO2 capture on the negatively charged χ3-borophene is 1.6 × 1014 e cm-2. The CO2 capture capacity of χ3-borophene is 4.09 × 1014 cm-2. Finally, we study the selectivity of negatively charged χ3-borophene. The results show that the negatively-charged χ3-borophene possesses a high selectivity for CO2 from its mixtures with CO, CH4, NH3, N2, H2S, and H2. χ3-borophene is a new promising charge-modulated switchable CO2 capture material with good stability, high CO2 capture capacity, high selectivity, and excellent electrical conductivity. more...

Tungsten (W) was considered as one important candidate for the magnetically constrained plasma first wall materials. The H impurities have a strong influence on the mechanical and thermal propertie... more...

Recently, Hu et al. reported that Ca2N monolayer is a good anode material for Na storage, but Li storage is not allowed since Li adsorption on Ca2N monolayer is energetically unfavorable. In this paper, from first-principles calculations, we predict that Li storage becomes possible when the Ca2N monolayer is rolling up into nanotubes. The curvature effect of the Ca2N nanotube decreases the Li adsorption energy to a level below 0 eV, corresponding to positive charge/discharge potential. As a result, Li storage in Ca2N nanotubes becomes feasible and a theoretical capacity of about 426.9 mAh/g is predicted for the Ca2N-(14, 0) nanotube. The metallic electronic structure and very fast Li/Na diffusion in the Ca2N nanotubes ensure that the rate performance of the Ca2N nanotubes can be good. This study offers an example of designing electrode materials for Li/Na ion batteries through curvature effect, and the strategy is applicable to other 2D materials. more...

The superstructure of χ3 borophene on Ag (111) has recently been synthesized in experiment. In this work, we investigate its structural, electronic properties and the oxidation mechanism through first-principles calculations. We find the superstructure of χ3 borophene on Ag (111) maintain the planar characteristics, like its free-standing form, owing to the weakly interaction between adsorbate and substrate. Moreover, oxygen molecule can be spontaneously adsorbed on its superstructure in a manner of chemical adsorption. Importantly, the energy barrier of ∼0.35 eV for oxygen dissociation indicates its relative stability in ambient conditions compared with the active silicene. Furthermore, the mobility of O2-dissociation-induced O atom is poor at room temperature, implying the difficult migration of O atom on borophene surface. On the other hand, due to the strong B O bonding, desorption of O2-dissociation-induced O atoms on superstructure of χ3 borophene becomes impossible, ultimately leading to form the boron oxides. more...

A collection of GdF3 core-shell structured (CSS) phosphors were synthesized by hydrothermal method. The as-prepared (AP) phosphors were coated with SiO2 layers to avoid aggregation and sintering during thermal annealing at 800 °C, after which the SiO2 layers were etched off and the annealed phosphors became highly dispersible. The annealed CSS phosphor aGdF3:Eu3+@GdF3:Ce3+,Dy3+ shows excellent multicolor luminescence performance with the aid of dual-channel excitation and energy migration (EM) procedure of Gd3+ ions. By inserting pyromellitic acid (PMA) organic ligands into the interfaces between annealed core and AP shell layer regions, the so-called antenna effect of organic ligands of PMA forms a new excitation channel, which makes the CSS phosphor aGdF3:Eu3+@PMA@GdF3:Ce3+,Dy3+ exhibit significantly enhanced multicolor luminescence via multi-channel excitation and EM process. The prepared CSS phosphors in this work are excellent candidates for applications in solid-state lighting. more...

The oxygen adsorption and dissociation on two types of free-standing borophene (β12 and χ3 phases) are studied through first-principles calculations. We find that oxygen molecule can be spontaneously and chemically adsorbed on free-standing borophene to lower the energy of the system. However, in contrast with the exceedingly unstable silicene in ambient conditions, β12 and χ3 borophene are relatively inactive due to an energy barrier for O2 dissociation of about 0.36 eV in β12 phase and 0.39 eV in χ3 phase, partly implying its chemical stability in oxygen. Moreover, the migration and desorption of O2-dissociation-induced O atoms at room temperature are very difficult due to the strong B O bonding in the O-adsorbed borophene, which is in favor of forming boron oxides ultimately. Our results reveal the interaction between borophene and O2 and suggest the enhanced stability of β12 and χ3 borophene in oxygen compared with silicene. more...

Using the first-principles methods, we investigated the structure, the mechanical properties, and solution and diffusion behavior of hydrogen impurity in the W-Ti lattice. The single H atom is energetically favorable sitting at the tetrahedral interstitial site nearest neighboring to the Ti atom in the W-Ti lattice. The minimum solution energy is about 0.498 eV. By analyzing the energy barrier curves, it is shown that the effect of titanium-doped tungsten on hydrogen migration behavior is small in the W-Ti lattice. Base on the elastic constants analysis, titanium-doped tungsten can withstand the degradation of mechanical strength induced by hydrogen effect. On the other hand, it is found that the ductility of pure W metal and W-Ti alloys can be improved substantially by hydrogen effect from the B/G ratio and the Poisson's ratio ν. However, the effect of the improved ductility is more obvious in the bcc pure W metal than that in the W-Ti alloys. more...

A collection of β-NaGdF 4 core-shell structured (CSS) phosphors were synthesized by Hydrothermal method, both the core and shell regions of which are hexagonal phase. The as-prepared core particles have the microrods shape, and the shell was formed upon them via epitaxial growth. After thermal annealing treatment of the core phosphors at 600 °C, the corresponding core-shell structure can still be effectively constructed. The photoluminescence (PL) spectra reveal that the CSS phosphors grown upon the as-prepared core particles own superior luminescent properties; for the annealed CSS phosphor β-NaGdF 4 :Eu 3+ @β-NaGdF 4 , a large amount of defects existed on the interfaces between the core and shell regions severely quenched the emission intensity of the core region; on co-doped Ce 3+ and Dy 3+ ions into the null shell layer of the annealed CSS phosphor, the obtained phosphor shows excellent multicolor luminescence performance due to quenching phenomenon effectively suppressed by dual-channel excitation and energy migration procedure of Gd 3+ ions. The prepared CSS phosphors in this work are excellent candidates for applications in solid-state lighting. more...

A theoretical investigation of ion-acoustic solitons in an unmagnetized plasma consisting of cold ions and regularized κ-distributed electrons has been carried out. The properties of stationary solitary structures are briefly studied by the reductive perturbation method in the small amplitude limit. It is found that in the small κ region, the ion-acoustic solitary waves propagate more slowly in the case of regularized κ distribution than in the case of standard κ distribution. The regularized κ-distributed electrons affect the width and amplitude of the solitary waves. As the cutoff parameter α increases, the amplitudes of both the compressive and rarefactive solitary waves decrease, and their widths also decrease. In addition, for a given value of κ, positive potential solitons will appear at large α, while negative potential solitons will appear at small α. The results of this paper may be useful for understanding nonlinear electrostatic phenomena in space plasmas. more...

An eight-channel poloidal correlation reflectometer (PCR) with O-mode polarization has been installed in the EAST tokamak to measure the fluctuations from core to edge. The PCR launches eight different frequency microwaves (20.4, 24.8, 33, 40, 42.4, 48, 52.6, 57.2 GHz) into the plasma from the low field side and two poloidally separated antennae are used to receive the reflected waves. As a result, the diagnostic can measure fluctuations in eight (radial)× two (poloidal) spatial positions. The diagnostic has been applied to study the core and edge pedestal fluctuations during an inter-ELM phase in H-mode plasma. This inter-ELM phase can be divided into two stages. In the first stage, a low frequency ( more...

The dispersion and damping rate of the ion acoustic waves (IAWs) in deuterium–tritium (D–T) fusion plasmas with slowing-down distributed α particles are investigated within the framework of kinetic theory. It is shown that the concentration of α particles has an important effect on IAWs. The frequency of IAWs decreases as the α concentration increases. Inversely, the damping rate increases as the α concentration increases. The results for slowing-down distributed α particles are compared with those obtained when α particles are assumed to have an equivalent Maxwellian distribution. more...

We investigated the structural and mechanical properties, the solution and diffusion behavior of carbon atom in the W–Ti lattice from first-principles calculations. The single C atom is energetically most favorable sitting at the octahedral interstitial site (OIS) nearest neighboring to the Ti atom in the W–Ti lattice. The minimum solution energy is about 0.874 eV. It is shown that the effect of titanium doping on the carbon migration behavior is small, while the migration energy barrier is quite high, and the highest energy barrier is up to 1.60 eV. Based on the elastic constants analysis, titanium doping tungsten can compensate the degradation of mechanical strength induced by carbon impurities. On the other hand, it is found that the ductility of pure W metal and W–Ti alloys is improved substantially by carbon impurities from the B/G ratio and the Poisson's ratio ν. The effect of the improved ductility is more obvious in pure W than that in the W–Ti alloys. In addition, substitutional C atom is better than interstitial C atom in terms of enhancing the ductility of pure W. more...

In this work, a computational modeling study on the mechanism of the acceleration behavior of a plasma bullet in needle-plane configuration is presented. Above all, in our model, two sub-models of time-dependent plasma dynamics and laminar flow are connected using a oneway coupled method, and both the working gas and the surrounding gas around the plasma jet are assumed to be the same, which are premixed He/N2 gas. The mole fractions of the N2 (NMF) ingredient are set to be 0.01%, 0.1% and 1% in three cases, respectively. It is found that in each case, the plasma bullet accelerates with time to a peak velocity after it exits the nozzle and then decreases until getting to the treated surface, and that the velocity of the plasma bullet increases at each time moment with the peak value changing from 0.72×106 m/s to 0.80×106 m/s but then drops more sharply when the NMF varies from 0.01% to 1%. Besides, the electron impact ionizations of helium neutrals and nitrogen molecules are found to have key influences on the propagation of a plasma bullet instead of the penning ionization. more...

The effect of Ti concentration on the fundamental mechanical properties of W-Ti alloys has been studied from first principles calculations. The lattice constants, the cell volumes and the formation energies of the W1-xTix (x = 0.0625, 0.125, 0.1875, 0.25, 0.5) alloys were calculated. It is shown that Ti alloying in bcc W lattice is thermodynamically favorable when the Ti concentration is lower than 25% and the W0.8125Ti0.1875 have the lowest formation energy. With the optimized geometry and lattice, the elastic constants are calculated and then the elastic moduli and other mechanical parameters are derived. Results show that although the mechanical strength of the W-Ti alloys is lower than that of pure W metal, it is much higher than that of pure Ti metal. On the other hand, the B/G ratio and the Poisson's ratio of the W-Ti alloys is much higher than that of pure W, and even higher than that of pure Ti, indicating that Ti alloying can improve the ductility of bcc W substantially. more...

Quaternary carbide Ti3NiAl2C ceramics has been investigated as a potential nuclear fusion structural material, and it has advantages in certain aspects compared with Ti2AlC, Ti3AlC2, and Ti3SiC2 structural materials. In this paper, quaternary carbide Ti3NiAl2C ceramics is pressurized to investigate its structural, mechanical, electronic properties, and Debye temperature. Quaternary carbide Ti3NiAl2C ceramics still maintains a cubic structure under pressure (0–110 GPa). At zero pressure, quaternary carbide Ti3NiAl2C ceramics only has three bonds: Ti–Al, Ni–Al, and Ti–C. However, at pressures of 20 GPa, 30 GPa, 40 GPa, 60 GPa, and 70 GPa, new Ti–Ni, Ti–Ti, Al–Al, Ti–Al, and Ti–Ti bonds form. When the pressure reaches 20 GPa, the covalent bonds change to metallic bonds. The volume of quaternary carbide Ti3NiAl2C ceramics can be compressed to 72% of its original volume at most. Pressurization can improve the mechanical strength and ductility of quaternary carbide Ti3NiAl2C ceramics. At 50–60 GPa, its mechanical strength can be comparable to pure tungsten, and the material changes from brittleness to ductility. However, the degree of anisotropy of quaternary carbide Ti3NiAl2C ceramics increases with the increasing pressure. In addition, we also investigated the Debye temperature, density, melting point, hardness, and wear resistance of quaternary carbide Ti3NiAl2C ceramics under pressure. more...