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<jats:p>Evolution of the charged grains in a two-dimensional dusty plasma under a spatially harmonic external force, in particular, their long-time behaviors after the force has been withdrawn, is studied by using molecular dynamics simulation. Under an external force and a grain–grain interaction force, initially homogeneously distributed grains can reach a quasi-stationary state in the form of a disk crystal. After the external force is withdrawn, the disk moves initially with its size and shape nearly unchanged until it rapidly stops moving, and eventually the disk grain rotates like a vortex. The time needed to reach the final state increases with the strength of the initial external force increasing.</jats:p>

<jats:p>The magnetic merging process related to pairwise magnetic islands coalescence is investigated by two-dimensional particle-in-cell simulations with a guide field. Owing to the force of attraction between parallel currents within the initial magnetic islands, the magnetic islands begin to approach each other and merge into one big island. We find that this newly formed island is unstable and can be divided into two small magnetic islands spontaneously. Lastly, these two small islands merge again. We follow the time evolution of this process, in which the contributions of three mechanisms of electron acceleration at different stages, including the Fermi, parallel electric field, and betatron mechanisms, are studied with the guide center theory.</jats:p>

<jats:p>Electromagnetic pulses (EMPs) produced by the interaction of a TW femtosecond laser with solid targets at the Compact Laser Plasma Accelerator (CLAPA) are measured and interpreted. The statistical results confirm that the intensities of the EMPs are closely related to both target material and thickness. The signal of the titanium target is more abundant than that of the copper target with the same thickness, and the intensity of EMP is positively correlated with the target thickness for aluminium foil. With the boosted EMP radiations, the energy of accelerated protons is also simultaneously enhanced. In addition, EMPs emitted from the front of the target exceed those from the rear, which are also pertinent to the specific target position. The resonant waveforms in the target chamber are analyzed using the fast Fourier transform, and the local resonance and the attenuation lead to changes of the frequency spectra of EMPs with variation of detecting positions, which is well supported by the modeling results. The findings are beneficial to gaining insight into the mechanism of EMP propagation in a typical target chamber and providing more information for EMP shielding design.</jats:p>

<jats:p>Based on the first-principles method, we predict two new stable BN allotropes: C12-BN and O16-BN, which belong to cubic and orthorhombic crystal systems, respectively. It is confirmed that both the phases are thermally and dynamically stable. The results of molecular dynamics simulations suggest that both the BN phases are highly stable even at high temperatures of 1000 K. In the case of mechanical properties, C12-BN has a bulk modulus of 359 GPa and a hardness of 43.4 GPa, making it a novel superhard material with potential technological and industrial applications. Electronic band calculations reveal that both C12-BN and O16-BN are insulators with direct band gaps of 3.02 eV and 3.54 eV, respectively. The XRD spectra of C12-BN and O16-BN are also simulated to provide more information for possible experimental observation. Our findings enrich the BN allotrope family and are expected to stimulate further experimental interest.</jats:p>

<jats:p>Kinetic behaviors of niobium and titanium carbide precipitates in iron are simulated with cluster dynamics. The simulations, carried out in austenite and ferrite for niobium carbides, and in austenite for titanium carbide, are analyzed for dependences on temperature, solute concentration, and initial cluster distribution. The results are presented for different temperatures and solute concentrations, compared to experimental data available. They show little impact of initial cluster distribution beyond a certain relaxation time and that highly dilute alloys with monomers only present a significantly different behavior from denser alloys or ones with different initial cluster distributions.</jats:p>

<jats:p>Silicon is a preferred material in solar cells, and most of silicon allotropes have an indirect band gap. Therefore, it is important to find new direct band gap silicon. In the present work, a new direct band gap silicon allotrope of <jats:italic>o</jats:italic>-Si32 is discovered. The elastic constants, elastic anisotropy, phonon spectra, and electronic structure of <jats:italic>o</jats:italic>-Si32 are obtained using first-principles calculations. The results show that <jats:italic>o</jats:italic>-Si32 is mechanically and dynamically stable and is a direct semiconductor material with a band gap of 1.261 eV.</jats:p>

<jats:p>Two novel non-isoelectronic with diamond (non-IED) B–C–O phases (tI16-B<jats:sub>8</jats:sub>C<jats:sub>6</jats:sub>O<jats:sub>2</jats:sub> and mP16-B<jats:sub>8</jats:sub>C<jats:sub>5</jats:sub>O<jats:sub>3</jats:sub>) have been unmasked. The research of the phonon scattering spectra and the independent elastic constants under ambient pressure (AP) and high pressure (HP) proves the stability of these non-IED B–C–O phases. Respective to the common compounds, the research of the formation enthalpies and the relationship with pressure of all non-IED B–C–O phases suggests that HP technology performed in the diamond anvil cell (DAC) or large volume press (LVP) is an important technology for synthesis. Both tI16-B<jats:sub>8</jats:sub>C<jats:sub>6</jats:sub>O<jats:sub>2</jats:sub> and tI12-B<jats:sub>6</jats:sub>C<jats:sub>4</jats:sub>O<jats:sub>2</jats:sub> possess electrical conductivity. mP16-B<jats:sub>8</jats:sub>C<jats:sub>5</jats:sub>O<jats:sub>3</jats:sub> is a small bandgap semiconductor with a 0.530 eV gap. For aP13-B<jats:sub>6</jats:sub>C<jats:sub>2</jats:sub>O<jats:sub>5</jats:sub>, mC20-B<jats:sub>2</jats:sub>CO<jats:sub>2</jats:sub> and tI18-B<jats:sub>4</jats:sub>CO<jats:sub>4</jats:sub> are all large gap semiconductors with gaps of 5.643 eV, 6.113 eV, and 7.105 eV, respectively. The study on the relationship between band gap values and pressure of these six non-IED B–C–O phases states that tI16-B<jats:sub>8</jats:sub>C<jats:sub>6</jats:sub>O<jats:sub>2</jats:sub> and tI12-B<jats:sub>6</jats:sub>C<jats:sub>4</jats:sub>O<jats:sub>2</jats:sub> maintain electrical conductivity, mC20-B<jats:sub>2</jats:sub>CO<jats:sub>2</jats:sub> and tI18-B<jats:sub>4</jats:sub>CO<jats:sub>4</jats:sub> have good bandgap stability and are less affected by pressure. The stress-strain simulation reveals that the max strain and stress of 0.4 GPa and 141.9 GPa respectively, can be sustained by tI16-B<jats:sub>8</jats:sub>C<jats:sub>6</jats:sub>O<jats:sub>2</jats:sub>. Studies on their mechanical properties shows that they all possess elasticity moduli and hard character. And pressure has an obvious effect on their mechanical properties, therein toughness of tI12-B<jats:sub>6</jats:sub>C<jats:sub>4</jats:sub>O<jats:sub>2</jats:sub>, aP13-B<jats:sub>6</jats:sub>C<jats:sub>2</jats:sub>O<jats:sub>5</jats:sub>, mC20-B<jats:sub>2</jats:sub>CO<jats:sub>2</jats:sub> and tI18-B<jats:sub>4</jats:sub>CO<jats:sub>4</jats:sub> all increases, and hardness of mP16-B<jats:sub>8</jats:sub>C<jats:sub>5</jats:sub>O<jats:sub>3</jats:sub> continue to strengthen during the compression. With abundant hardness characteristics and tunable band gaps, extensive attention will be focused on the scientific research of non-IED B–C–O compounds.</jats:p>

<jats:p>Three-dimensional type-II Weyl fermions possess overtilted cone-like low-energy band dispersion. Unlike the closed ellipsoidal Fermi surface for type-I Weyl fermions, the Fermi surface is an open hyperboloid for type-II Weyl fermions. We evaluate the spin and density susceptibility of type-II Weyl fermions with repulsive S-wave interaction by means of Green’s functions. We obtain the particle–hole continuum along the tilted momentum direction and perpendicular to the tilted momentum direction respectively. We find the zero sound mode in some repulsive interaction strengths by numerically solving the pole equations of the susceptibility within the random-phase approximation.</jats:p>

<jats:p>We analytically and numerically study a 1D tight-binding model with tunable incommensurate potentials. We utilize the self-dual relation to obtain the critical energy, namely, the mobility edge. Interestingly, we analytically demonstrate that this critical energy is a constant independent of strength of potentials. Then we numerically verify the analytical results by analyzing the spatial distributions of wave functions, the inverse participation rate and the multifractal theory. All numerical results are in excellent agreement with the analytical results. Finally, we give a brief discussion on the possible experimental observation of the invariable mobility edge in the system of ultracold atoms in optical lattices.</jats:p>

<jats:p>The lead-free perovskites Cs<jats:sub>3</jats:sub> <jats:italic>B</jats:italic> <jats:sub>2</jats:sub> <jats:italic>X</jats:italic> <jats:sub>9</jats:sub> (<jats:italic>B</jats:italic> = Sb, Bi; <jats:italic>X</jats:italic> = Cl, Br, I) as the popular photoelectric materials have excellent optical properties with lower toxicity. In this study, we systematically investigate the stable monolayer Cs<jats:sub>3</jats:sub> <jats:italic>B</jats:italic> <jats:sub>2</jats:sub> <jats:italic>X</jats:italic> <jats:sub>9</jats:sub> and bilayer vertical heterostructure Cs<jats:sub>3</jats:sub> <jats:italic>B</jats:italic> <jats:sub>2</jats:sub> <jats:italic>X</jats:italic> <jats:sub>9</jats:sub>/Cs<jats:sub>3</jats:sub> <jats:inline-formula> <jats:tex-math> <?CDATA $B_2^\prime $?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>B</mml:mi> <mml:mn>2</mml:mn> <mml:mo>′</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_31_2_027102_ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> <jats:italic>X</jats:italic> <jats:sub>9</jats:sub> (<jats:italic>B,</jats:italic> <jats:italic>B′</jats:italic> = Sb, Bi; <jats:italic>X</jats:italic> = Cl, Br, I) via first-principles simulations. By exploring the electrical structures and band edge positions, we find the band gap reduction and the band type transition in the heterostructure Cs<jats:sub>3</jats:sub> <jats:italic>B</jats:italic> <jats:sub>2</jats:sub> <jats:italic>X</jats:italic> <jats:sub>9</jats:sub>/Cs<jats:sub>3</jats:sub> <jats:inline-formula> <jats:tex-math> <?CDATA $B_2^\prime $?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>B</mml:mi> <mml:mn>2</mml:mn> <mml:mo>′</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_31_2_027102_ieqn4.gif" xlink:type="simple" /> </jats:inline-formula> <jats:italic>X</jats:italic> <jats:sub>9</jats:sub> due to the charge transfer between layers. Furthermore, the results of optical properties reveal light absorption from the visible light to UV region, especially monolayer Cs<jats:sub>3</jats:sub>Sb<jats:sub>2</jats:sub>I<jats:sub>9</jats:sub> and heterostructure Cs<jats:sub>3</jats:sub>Sb<jats:sub>2</jats:sub>I<jats:sub>9</jats:sub>/Cs<jats:sub>3</jats:sub>Bi<jats:sub>2</jats:sub>I<jats:sub>9</jats:sub>, which have absorption peaks in the visible light region, leading to the possibility of photocatalytic water splitting. These results provide insights for more two-dimensional semiconductors applied in the optoelectronic and photocatalytic fields.</jats:p>