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<jats:p>Ionic liquids usually behave as fragile liquids, and the temperature dependence of their dynamic properties obeys supper-Arrhenius law. In this work, a dynamic crossover is observed in ([VIO<jats:sup>2+</jats:sup>][Tf<jats:sub>2</jats:sub>N<jats:sup>−</jats:sup>]<jats:sub>2</jats:sub>) ionic liquid at the temperature of 240–800 K. The diffusion coefficient does not obey a single Arrhenius law or a Vogel–Fulcher–Tammann (VFT) relation, but can be well fitted by three Arrhenius laws or a combination of a VFT relation and an Arrhenius law. The origin of the dynamic crossover is analyzed from correlation, structure, and thermodynamics. Ion gets a stronger backward correlation at a lower temperature, as shown by the fractal dimension of the random walk. The temperature dependence function of fractal dimension, heterogeneity order parameter, and thermodynamic data can be separated into three regions similar to that observed in the diffusion coefficient. The two crossover temperatures observed in the three types of data are almost the same as that in diffusion coefficient fitted by three Arrhenius laws. The results indicate that the dynamic crossover of [VIO<jats:sup>2+</jats:sup>][Tf<jats:sub>2</jats:sub>N<jats:sup>−</jats:sup>]<jats:sub>2</jats:sub> is attributed to the heterogeneous structure when it undergoes cooling.</jats:p>

<jats:p>Lithium-ion batteries suffer from mechano–electrochemical coupling problems that directly determine the battery life. In this paper, we investigate the electrode electrochemical performance under stress conditions, where seven tensile/compressive stresses are designed and loaded on electrodes, thereby decoupling mechanics and electrochemistry through incremental stress loads. Four types of multi-group electrochemical tests under tensile/compressive stress loading and normal package loading are performed to quantitatively characterize the effects of tensile stress and compressive stress on cycle performance and the kinetic performance of a silicon composite electrode. Experiments show that a tensile stress improves the electrochemical performance of a silicon composite electrode, exhibiting increased specific capacity and capacity retention rate, reduced energy dissipation rate and impedances, enhanced reactivity, accelerated ion/electron migration and diffusion, and reduced polarization. Contrarily, a compressive stress has the opposite effect, inhibiting the electrochemical performance. The stress effect is nonlinear, and a more obvious suppression via compressive stress is observed than an enhancement via tensile stress. For example, a tensile stress of 675 kPa increases diffusion coefficient by 32.5%, while a compressive stress reduces it by 35%. Based on the experimental results, the stress regulation mechanism is analyzed. Tensile stress loads increase the pores of the electrode material microstructure, providing more deformation spaces and ion/electron transport channels. This relieves contact compressive stress, strengthens diffusion/reaction, and reduces the degree of damage and energy dissipation. Thus, the essence of stress enhancement is that it improves and optimizes diffusion, reaction and stress in the microstructure of electrode material as well as their interactions via physical morphology.</jats:p>

<jats:p>The temperature in the high-pressure high-temperature (HPHT) synthesis is optimized to enhance the thermoelectric properties of high-density ZnO ceramic, Zn<jats:sub>0.98</jats:sub>Al<jats:sub>0.02</jats:sub>O. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy show that HPHT can be utilized to control the crystal structure and relative density of the material. High pressure can be utilized to change the energy band structure of the samples via changing the lattice constant of samples, which decreases the thermal conductivity due to the formation of a multi-scale hierarchical structure and defects. The electrical conductivity of the material reaches 6 × 10<jats:sup>4</jats:sup> S/m at 373 K, and all doped samples behave as n-type semiconductors. The highest power factor (6.42 μW ⋅ cm<jats:sup>−1</jats:sup>⋅K<jats:sup>−2</jats:sup>) and dimensionless figure of merit (<jats:italic>zT</jats:italic> = 0.09) are obtained when Zn<jats:sub>0.98</jats:sub>Al<jats:sub>0.02</jats:sub>O is produced at 973 K using HPHT, which is superior to previously reported power factors for similar materials at the same temperature. Hall measurements indicate a high carrier concentration, which is the reason for the enhanced electrical performance.</jats:p>

<jats:p>We theoretically study the structural, elastic and optical properties of ErPdBi together with its anisotropic behaviors using density functional theory. It is observed that ErPdBi satisfies the Born stability criteria nicely and possesses high quality of machinability. The anisotropic behavior of ErPdBi is reported with the help of theoretical anisotropy indices incorporating 3D graphical presentation, which suggests that ErPdBi is highly anisotropic in nature. It is noticed that the minimum thermal conductivity is very low for ErPdBi compared to the several species. This low value of minimum thermal conductivity introduces the potentiality of ErPdBi in high-temperature applications such as thermal barrier coatings. In addition, deep optical insights of ErPdBi reveal that our material can be used in different optoelectronic and electronic device applications ranging from organic light-emitting diodes, solar panel efficiency, waveguides etc. to integration of integrated circuits. Therefore, we believe that our results will provide a new insight into high-temperature applications and will benefit for the development of promising optoelectric devices as well.</jats:p>

<jats:p>The high-frequency edge of the first-order Raman mode of diamond reflects the stress state at the culet of anvil, and is often used for the pressure calibration in diamond anvil cell (DAC) experiments. Here we point out that the high-frequency edge of the diamond Raman phonon corresponds to the Brillouin zone (BZ) center <jats:italic>Γ</jats:italic> point as a function of pressure. The diamond Raman pressure gauge relies on the stability of crystal lattice of diamond under high stress. Upon the diamond anvil occurs failure under the uniaxial stress (197 GPa), the loss of intensity of the first-order Raman phonon and a stress-dependent broad Raman band centered at 600 cm<jats:sup>−1</jats:sup> are observed, which is associated with a strain-induced local mode corresponding to the BZ edge phonon of the <jats:italic>L</jats:italic> <jats:sub>1</jats:sub> transverse acoustic phonon branch.</jats:p>

<jats:p>Novel chalcogenide glasses of pseudo-binary (100 – <jats:italic>x</jats:italic>)Sb<jats:sub>2</jats:sub>S<jats:sub>3</jats:sub>–<jats:italic>x</jats:italic>CuI systems were synthesized by traditional melt-quenching method. The glass-forming region of Sb<jats:sub>2</jats:sub>S<jats:sub>3</jats:sub>-CuI system was determined ranging from <jats:italic>x</jats:italic> = 30 mol% to 40 mol%. CuI acts as a non-bridging modifier to form appropriate amount of [SbSI] structural units for improving the glass-forming ability of Sb<jats:sub>2</jats:sub>S<jats:sub>3</jats:sub>. Particularly, as-prepared glassy sample is able to transmit light beyond 14 μm, which is the wider transparency region than most sulfide glasses. Their physical properties, including Vickers hardness (<jats:italic>H</jats:italic> <jats:sub>v</jats:sub>), density (<jats:italic>ρ</jats:italic>), and ionic conductivity (<jats:italic>σ</jats:italic>) were characterized and analyzed with the compositional-dependent Raman spectra. These experimental results would provide useful knowledge for the development of novel multi-spectral optical materials and glassy electrolytes.</jats:p>

<jats:p>The robustness of infrastructure networks has attracted great attention in recent years. Scholars have studied the robustness of complex networks against cascading failures from different aspects. In this paper, a new capacity allocation strategy is proposed to reduce cascading failures and improve network robustness without changing the network structure. Compared with the typical strategy proposed in Motter–Lai (ML) model, the new strategy can reduce the scale of cascading failure. The new strategy applied in scale-free network is more efficient. In addition, to reasonably evaluate the two strategies, we introduce contribution rate of unit capacity to network robustness as evaluation index. Results show that our new strategy works well, and it is more advantageous in the rational utilization of capacity in scale-free networks. Furthermore, we were surprised to find that the efficient utilization of capacity costs declined as costs rose above a certain threshold, which indicates that it is not wise to restrain cascading failures by increasing capacity costs indefinitely.</jats:p>

<jats:p>GaTe is a two-dimensional III–VI semiconductor with suitable direct bandgap of ∼ 1.65 eV and high photoresponsivity, which makes it a promising candidate for optoelectronic applications. GaTe exists in two crystalline phases: monoclinic (m-GaTe, with space group <jats:italic>C</jats:italic>2/<jats:italic>m</jats:italic>) and hexagonal (h-GaTe, with space group <jats:italic>P</jats:italic>63/<jats:italic>mmc</jats:italic>). The phase transition between the two phases was reported under temperature-varying conditions, such as annealing, laser irradiation, etc. The explicit phase transition temperature and energy barrier during the temperature-induced phase transition have not been explored. In this work, we present a comprehensive study of the phase transition process by using first-principles energetic and phonon calculations within the quasi-harmonic approximation framework. We predicted that the phase transition from h-GaTe to m-GaTe occurs at the temperature decreasing to 261 K. This is in qualitative agreement with the experimental observations. It is a two-step transition process with energy barriers 199 meV and 288 meV, respectively. The relatively high energy barriers demonstrate the irreversible nature of the phase transition. The electronic and phonon properties of the two phases were further investigated by comparison with available experimental and theoretical results. Our results provide insightful understanding on the process of temperature-induced phase transition of GaTe.</jats:p>

<jats:p>With the formation of structural vacancies, zirconium nitrides (key materials for cutting coatings, super wear-resistance, and thermal barrier coatings) display a variety of compositions and phases featuring both cation and nitrogen enrichment. This study presents a systematic exploration of the stable crystal structures of zirconium heminitride combining the evolutionary algorithm method and <jats:italic>ab initio</jats:italic> density functional theory calculations at pressures of 0 GPa, 30 GPa, 60 GPa, 90 GPa, 120 GPa, 150 GPa, and 200 GPa. In addition to the previously proposed phases <jats:italic>P</jats:italic>4<jats:sub>2</jats:sub>/<jats:italic>mnm</jats:italic>-, <jats:italic>Pnnm</jats:italic>-, and <jats:italic>Cmcm</jats:italic>-Zr<jats:sub>2</jats:sub>N, five new high-pressure Zr<jats:sub>2</jats:sub>N phases of <jats:italic>P</jats:italic>4/<jats:italic>nmm</jats:italic>, <jats:italic>I</jats:italic>4/<jats:italic>mcm</jats:italic>, <jats:italic>P</jats:italic>2<jats:sub>1</jats:sub>/<jats:italic>m</jats:italic>, <jats:inline-formula> <jats:tex-math><?CDATA $P\bar{3}m1$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>P</mml:mi> <mml:mover accent="true"> <mml:mn>3</mml:mn> <mml:mo>¯</mml:mo> </mml:mover> <mml:mi>m</mml:mi> <mml:mn>1</mml:mn> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_30_1_016403_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, and <jats:italic>C</jats:italic>2/<jats:italic>m</jats:italic> are discovered. An enthalpy study of these candidate configurations reveals various structural phase transformations of Zr<jats:sub>2</jats:sub>N under pressure. By calculating the elastic constants and phonon dispersion, the mechanical and dynamical stabilities of all predicted structures are examined at ambient and high pressures. To understand the structure–property relationships, the mechanical properties of all Zr<jats:sub>2</jats:sub>N compounds are investigated, including the elastic moduli, Vickers hardness, and directional dependence of Young’s modulus. The <jats:italic>Cmcm</jats:italic>-Zr<jats:sub>2</jats:sub>N phase is found to belong to the brittle materials and has the highest Vickers hardness (12.9 GPa) among all candidate phases, while the <jats:italic>I</jats:italic>4/<jats:italic>mcm</jats:italic>-Zr<jats:sub>2</jats:sub>N phase is the most ductile and has the lowest Vickers hardness (2.1 GPa). Furthermore, the electronic mechanism underlying the diverse mechanical behaviors of Zr<jats:sub>2</jats:sub>N structures is discussed by analyzing the partial density of states.</jats:p>

<jats:p>In 1949, Tolman found the relation between the surface tension and Tolman length, which determines the dimensional effect of the surface tension. Tolman length is the difference between the equimolar surface and the surface of tension. In recent years, the magnitude, expression, and sign of the Tolman length remain an open question. An incompressible and homogeneous liquid droplet model is proposed and the approximate expression and sign for Tolman length are derived in this paper. We obtain the relation between Tolman length and the radius of the surface of tension (<jats:italic>R</jats:italic> <jats:sub>s</jats:sub>) and found that they increase with the <jats:italic>R</jats:italic> <jats:sub>s</jats:sub> decreasing. The Tolman length of plane surface tends to zero. Taking argon for example, molecular dynamics simulation is carried out by using the Lennard–Jones (LJ) potential between atoms at a temperature of 90 K. Five simulated systems are used, with numbers of argon atoms being 10140, 10935, 11760, 13500, and 15360, respectively. By methods of theoretical study and molecular dynamics simulation, we find that the calculated value of Tolman length is more than zero, and it decreases as the size is increased among the whole size range. The value of surface tension increases with the radius of the surface of tension increasing, which is consistent with Tolman’s theory. These conclusions are significant for studying the size dependence of the surface tension.</jats:p>