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<jats:p>The influence of temperature on mode coupling effect in piezoelectric vibrators remains unclear. In this work, we discuss the influence of temperature on two-dimensional (2D) mode coupling effect and electromechanical coupling coefficient of cylindrical [001]<jats:sub> <jats:italic>c</jats:italic> </jats:sub>-poled Mn-doped 0.24PIN–0.46PMN–0.30PT piezoelectric single-crystal vibrator with an arbitrary configuration ratio. The electromechanical coupling coefficient <jats:italic>k</jats:italic> <jats:sub>t</jats:sub> decreases with temperature increasing, whereas <jats:italic>k</jats:italic> <jats:sub>33</jats:sub> is largely invariant in a temperature range of 25 °C–55 °C. With the increase of temperature, the shift in the ‘mode dividing point’ increases the scale of the poling direction of the piezoelectric vibrator. The temperature has little effect on coupling constant <jats:italic>Γ</jats:italic>. At a given temperature, the coupling constant <jats:italic>Γ</jats:italic> of the cylindrical vibrator is slightly greater than that of the rectangular vibrator. When the temperature changes, the applicability index (<jats:italic>M</jats:italic>) values of the two piezoelectric vibrators are close to 1, indicating that the coupling theory can be applied to piezoelectric vibrators made of late-model piezoelectric single crystals.</jats:p>

<jats:p>Reconnection electric field is a key element of magnetic reconnection. It quantifies the change of magnetic topology and the dissipation of magnetic energy. In this work, two-dimensional (2D) particle-in-cell (PIC) simulations are performed to study the growth of the reconnection electric field in the electron diffusion region (EDR) during magnetic reconnection with a guide field. At first, a seed electric field is produced due to the excitation of the tearing-mode instability. Then, the reconnection electric field in the EDR, which is dominated by the electron pressure tensor term, suffers a spontaneous growth stage and grows exponentially until it saturates. A theoretical model is also proposed to explain such a kind of growth. The reconnection electric field in the EDR is found to be directly proportional to the electron outflow speed. The time derivative of electron outflow speed is proportional to the reconnection electric field in the EDR because the outflow is formed after the inflow electrons are accelerated by the reconnection electric field in the EDR and then directed away along the outflow direction. This kind of reinforcing process at last leads to the exponential growth of the reconnection electric field in the EDR.</jats:p>

<jats:p>In order to provide detailed information about Cd structure and gain more insight regarding ionization degrees and types of transition, as well as the understanding of the temporal evolution behavior of laser produced Cd plasmas, extreme ultraviolet spectra of laser-produced cadmium (Cd) plasmas have been measured in the 8.4–12 nm region using spatio-temporally resolved laser-produced plasma spectroscopy technique. Spectral features were analyzed by the Hartree–Fock (HF) method with relativistic correlations (HFR) using the Cowan code. The results showed that the 4p–5s resonance transition arrays from Cd<jats:sup>9+</jats:sup> to Cd<jats:sup>13+</jats:sup> merged to form intense lines in this spectral region. A number of new spectral features from Cd<jats:sup>9+</jats:sup> and Cd<jats:sup>10+</jats:sup> ions are reported in this study. Based on the assumption of a normalized Boltzmann distribution among the excited states associated with a steady-state collisional–radiative model, the plasma parameters were obtained by comparing the experimental and simulated spectra. As a result, we succeeded in reproducing the synthetic spectra for different time delays, which yielded good agreement with the experiments. The temporal evolution behaviors of electron temperature and electron density of plasma were also analyzed.</jats:p>

<jats:p>The martensitic-type phase transformation paths from the rutile to the <jats:italic>α</jats:italic>-PbO<jats:sub>2</jats:sub> phase of TiO<jats:sub>2</jats:sub> are studied with linear interpolation and NEB/G-SSNEB methods based on first-principles calculations. Its potential energy surface and the lowest energy path are revealed. Our results indicate that the titanium atoms of the rutile phase shuffle along the [0–11]<jats:sub>rut</jats:sub> crystal direction to form the <jats:italic>α</jats:italic>-PbO<jats:sub>2</jats:sub> phase. During the phase transition, the oxygen atoms are dragged by the heavier titanium atoms and then reach their new equilibrium positions. The barrier of phase transition from nudged elastic band theory is about 231 meV, which is qualitatively consistent with previous theoretical calculations from the monoclinic phase to the tetragonal phase for ZrO<jats:sub>2</jats:sub> and HfO<jats:sub>2</jats:sub>. Debye model can also be successfully used to predict the pressure and temperature of the phase transformation.</jats:p>

<jats:p>Van der Waals (vdW) heterostructures have attracted significant attention because of their widespread applications in nanoscale devices. In the present work, we investigate the electronic structures of germanane/antimonene vdW heterostructure in response to normal strain and an external electric field by using the first-principles calculations based on density functional theory (DFT). The results demonstrate that the germanane/antimonene vdW heterostructure behaves as a metal in a [−1, −0.6] V/Å range, while it is a direct semiconductor in a [−0.5, 0.2] V/Å range, and it is an indirect semiconductor in a [0.3, 1.0] V/Å range. Interestingly, the band alignment of germanane/antimonene vdW heterostructure appears as type-II feature both in a [−0.5, 0.1] range and in a [0.3, 1] V/Å range, while it shows the type-I character at 0.2 V/Å. In addition, we find that the germanane/antimonene vdW heterostructure is an indirect semiconductor both in an in-plane biaxial strain range of [−5%, −3%] and in an in-plane biaxial strain range of [3%, 5%], while it exhibits a direct semiconductor character in an in-plane biaxial strain range of [−2%, 2%]. Furthermore, the band alignment of the germanane/antimonene vdW heterostructure changes from type-II to type-I at an in-plane biaxial strain of –3%. The adjustable electronic structure of this germanane/antimonene vdW heterostructure will pave the way for developing the nanoscale devices.</jats:p>

<jats:p>This article reviews the research progress of measurement techniques and materials on the mechanocaloric effect over the past few decades. Mechanocaloric materials can be divided into elastocaloric and barocaloric materials depending on the applied uniaxial stress or hydrostatic pressure. Elastocaloric materials include non-magnetic shape memory alloys, polymers, and rare-earth compounds. Barocaloric materials include magnetic shape memory alloys, ferroelectric ceramics, superionic conductors, and oxyfluorides. The mechanocaloric effects of these classes of materials are systematically compared in terms of the isothermal entropy change and adiabatic temperature change. In addition to the thermal effects, other characteristics closely related to the application of mechanocaloric materials are also summarized. Finally, perspectives for further development of mechanocaloric materials in the solid-state cooling area are discussed.</jats:p>

<jats:p>Controlling the alignment and packing structure of organic molecules on solid substrate surfaces at molecule level is essential to develop high-performance organic thin film (OTF) devices. Pentacene, which is a typical p-type semiconductor material usually adopts lying-down geometry on metal substrates owning to <jats:italic>π</jats:italic>–d coupling between pentacene and metal substrates. However, in this study, we found that pentacene molecules can be adsorbed on an anneal-treated Cu (111) surface with their long axis perpendicular to substrate surface. Highly ordered single-layer pentacene film with stand-up molecular geometry was achieved on this substrate. It was found that the functionalization of Cu surface with C = O groups due to annealing treatment should be accounted for standing-up geometry of pentacene on Cu substrate. This observation shed light on the tuning of the alignment and packing structure of organic molecules.</jats:p>

<jats:p>The stable geometries, electronic structures, and magnetic behaviors of the ScLi<jats:sub> <jats:italic>n</jats:italic> </jats:sub> (<jats:italic>n</jats:italic> = 2–13) clusters are investigated by using particle swarm optimization (PSO) and density functional theory (DFT). The results show that these clusters have three-dimensional (3D) structures except ScLi<jats:sub>2</jats:sub>, and ScLi<jats:sub>12</jats:sub>, and ScLi<jats:sub>13</jats:sub> that possess the cage-like structures. In analyses of the average binding energy, second-order difference of energy, and fragmentation energy, ScLi<jats:sub>12</jats:sub> cluster is identified as magnetic superatom. The magnetic moment for each of these clusters owns an oscillating curve of different cluster sizes, and their magnetic moments are further investigated using molecular orbitals and jellium model. Of ScLi<jats:sub> <jats:italic>n</jats:italic> </jats:sub> (<jats:italic>n</jats:italic> = 2–13) clusters, ScLi<jats:sub>12</jats:sub> has the largest spin magnetic moment (3 <jats:italic>μ</jats:italic> <jats:sub>B</jats:sub>), and molecular orbitals of ScLi<jats:sub>12</jats:sub> can be described as <jats:inline-formula> <jats:tex-math><?CDATA $1{{\rm{S}}}^{2}1{\rm{P}}{6}^{1}{{\rm{D}}}_{\alpha }^{5}{{\rm{D}}}_{\beta }^{2}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>1</mml:mn> <mml:msup> <mml:mi mathvariant="normal">S</mml:mi> <mml:mn>2</mml:mn> </mml:msup> <mml:mn>1</mml:mn> <mml:mi mathvariant="normal">P</mml:mi> <mml:msup> <mml:mn>6</mml:mn> <mml:mn>1</mml:mn> </mml:msup> <mml:msubsup> <mml:mi mathvariant="normal">D</mml:mi> <mml:mi>α</mml:mi> <mml:mn>5</mml:mn> </mml:msubsup> <mml:msubsup> <mml:mi mathvariant="normal">D</mml:mi> <mml:mi>β</mml:mi> <mml:mn>2</mml:mn> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_29_7_077101_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>. Additionally, Mulliken population and AdNDP bonding analysis are discussed and the results reveal that the Sc atom and Li<jats:sub> <jats:italic>n</jats:italic> </jats:sub> atoms make equal contribution to the total magnetic moment, and atomic charges transfer between Sc atoms and Li atoms.</jats:p>

<jats:p>The optical absorption of exciton interstate transition in Zn<jats:sub>1 − <jats:italic>xl</jats:italic> </jats:sub>Mg<jats:sub> <jats:italic>xl</jats:italic> </jats:sub>O/ZnO/Zn<jats:sub>1 − <jats:italic>xc</jats:italic> </jats:sub>Mg<jats:sub> <jats:italic>xc</jats:italic> </jats:sub>O/ZnO/Zn<jats:sub>1 − <jats:italic>xr</jats:italic> </jats:sub>Mg<jats:sub> <jats:italic>xr</jats:italic> </jats:sub>O asymmetric double quantum wells (ADQWs) with mixed phases of zinc-blende and wurtzite in Zn<jats:sub>1 − <jats:italic>x</jats:italic> </jats:sub>Mg<jats:sub> <jats:italic>x</jats:italic> </jats:sub>O for 0.37 &lt; <jats:italic>x</jats:italic> &lt; 0.62 is discussed. The mixed phases are taken into account by our weight model of fitting. The states of excitons are obtained by a finite difference method and a variational procedure in consideration of built-in electric fields (BEFs) and the Hartree potential. The optical absorption coefficients (OACs) of exciton interstate transition are obtained by the density matrix method. The results show that Hartree potential bends the conduction and valence bands, whereas a BEF tilts the bands and the combined effect enforces electrons and holes to approach the opposite interfaces to decrease the Coulomb interaction effects between electrons and holes. Furthermore, the OACs indicate a transformation between direct and indirect excitons in zinc-blende ADQWs due to the quantum confinement effects. There are two kinds of peaks corresponding to wurtzite and zinc-blende structures respectively, and the OACs merge together under some special conditions. The computed result of exciton interband emission energy agrees well with a previous experiment. Our conclusions are helpful for further relative theoretical studies, experiments, and design of devices consisting of these quantum well structures.</jats:p>