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<jats:p>Primary radiation damage in hcp Zr, including both defect production in a single collision cascade and damage buildup through cascade overlap, is investigated using molecular dynamics (MD) simulations from a potential energy landscape (PEL) perspective. It is found that the material’s response to an energetic particle can be understood as a trajectory in the PEL comprising a fast uphill journey and a slow downhill one. High-temperature-induced damage reduction and the difference in the radiation tolerance between metals and semiconductors can be both qualitatively explained by the dynamics of the trajectory associated with the topographic features of the system’s PEL. Additionally, by comparing irradiation and heating under a nearly identical condition, we find that large atomic displacements stemming from the extreme locality of the energy deposition in irradiation events are the key factor leading to radiation damage in a solid. Finally, we discuss the advantages of the PEL perspective and suggest that a combination of the PEL and the traditional crystallographic methods may provide more insights in future work.</jats:p>

<jats:p>Nanocrystalline samples of highly pure lead oxide were prepared by the sol-gel route of synthesis. X-ray diffraction and transmission electron microscopic techniques confirmed the nanocrystallinity of the samples, and the average sizes of the crystallites were found within 20 nm to 35 nm. The nanocrystallites exhibited specific anomalous properties, among which a prominent one is the increased lattice parameters and unit cell volumes. The optical band gaps also increased when the nanocrystallites became smaller in size. The latter aspect is attributable to the onset of quantum confinement effects, as seen in a few other metal oxide nanoparticles. Positron annihilation was employed to study the vacancy type defects, which were abundant in the samples and played crucial roles in modulating their properties. The defect concentrations were significantly larger in the samples of smaller crystallite sizes. The results suggested the feasibility of tailoring the properties of lead oxide nanocrystallites for technological applications, such as using lead oxide nanoparticles in batteries for better performance in discharge rate and resistance. It also provided the physical insight into the structural build-up process when crystallites were formed with a finite number of atoms, whose distributions were governed by the site stabilization energy.</jats:p>

<jats:p>In eight quadrants, the positive and negative signs of tensor components describing physical properties of biaxial crystals have been given. The distributions of the physical properties described with different order tensors and their space symmetries have been discussed. These results show that the distributions of effective physical constants are symmetrical in the eight quadrants for the orthorhombic system, but there are two and four kinds of distributions for monoclinic and triclinic systems respectively. Thence, to avoid ambiguities and difficulties in characterizing and applying properties of biaxial crystals, we suggest that the really positive directions of the coordinate axes should be defined before the measurements of their physical properties and their device applications.</jats:p>

<jats:p>We present a mechanically tunable broadband terahertz (THz) modulator based on the high-aligned Ni nanowire (NW) arrays. The modulator is a sandwich structure consisting of two polydimethylsiloxane layers and a central layer of high-aligned Ni NW arrays. Our experimental measurements reveal the transmittance of THz wave can be effectively modulated by mechanical stretching. The NW density in arrays increases with the strain increasing, which induced an enhancement in the absorption of THz wave. When the strain increases from 0 to 6.5%, a linear relationship is observed for the variation of modulation depth (MD) of THz wave regarding the strain, and the modulated range is from 0 to 85% in a frequency range from 0.3 THz to 1.8 THz. Moreover, the detectable MD is about 15% regarding the 1 % strain change resolution. This flexible Ni NW-based modulator can be promised many applications, such as remote strain sensing, and wearable devices.</jats:p>

<jats:p>Although tuning band structure of optoelectronic semiconductor-based materials by means of doping single defect is an important approach for potential photocatalysis application, C-doping or oxygen vacancy (Vo) as a single defect in ZnO still has limitations for photocatalytic activity. Meanwhile, the influence of co-existence of various defects in ZnO still lacks sufficient studies. Therefore, we investigate the photocatalytic properties of ZnO<jats:sub> <jats:italic>x</jats:italic> </jats:sub>C<jats:sub>0.0625</jats:sub> (<jats:italic>x</jats:italic> = 0.9375, 0.875, 0.8125), confirming that the co-effect of various defects has a greater enhancement for photocatalytic activity driven by visible-light than the single defect in ZnO. To clarify the underlying mechanism of co-existence of various defects in ZnO, we perform systematically the electronic properties calculations using density functional theory. It is found that the co-effect of C-doping and Vo in ZnO can achieve a more controllable band gap than doping solely in ZnO. Moreover, the impact of the effective masses of ZnO<jats:sub> <jats:italic>x</jats:italic> </jats:sub>C<jats:sub>0.0625</jats:sub> (<jats:italic>x</jats:italic> = 0.9375, 0.875, 0.8125) is also taken into account. In comparison with heavy Vo concentrations, the light Vo concentration (<jats:italic>x</jats:italic> = 0.875) as the optimal component together with C-doping in ZnO, can significantly improve the visible-light absorption and benefit photocatalytic activity.</jats:p>

<jats:p>The non-equilibrium dynamics of a one-dimensional (1D) topological system with 3rd-nearest-neighbor hopping has been investigated by analytical and numerical methods. An analytical form of topological defect density under the periodic boundary conditions (PBC) is obtained by using the Landau–Zener formula (LZF), which is consistent with the scaling of defect production provided by the Kibble–Zurek mechanism (KZM). Under the open boundary conditions (OBC), quench dynamics becomes more complicated due to edge states. The behaviors of the system quenching across different phases show that defect production no longer satisfies the KZM paradigm since complicated couplings exist under OBC. Some new dynamical features are revealed.</jats:p>

<jats:p>First principles calculation is performed to study the co-adsorption behaviors of O<jats:sub>2</jats:sub> and CO<jats:sub>2</jats:sub> on <jats:italic>δ</jats:italic>-Pu(100) surface by using a slab model within the framework of density functional theory (DFT). The results demonstrate that the most favorable co-adsorption configurations are T<jats:sub>v</jats:sub>-C<jats:sub>4</jats:sub>O<jats:sub>7</jats:sub> and T<jats:sub>p1</jats:sub>-C<jats:sub>2</jats:sub>O<jats:sub>8</jats:sub>, with adsorption energy of –17.296 eV and –23.131 eV for CO<jats:sub>2</jats:sub>-based and O<jats:sub>2</jats:sub>-based system, respectively. The C and O atoms mainly interact with the Pu surface atoms. Furthermore, the chemical bonding between C/O and Pu atom is mainly of ionic state, and the reaction mechanism is that C 2s, C 2p, O 2s, and O 2p orbitals overlap and hybridize with Pu 6p, Pu 6d, and Pu 5f orbital, resulting in the occurrence of new band structure. The adsorption and dissociation of CO<jats:sub>2</jats:sub> molecule are obviously promoted by preferentially occupying adsorbed O atoms, therefore, a potential CO<jats:sub>2</jats:sub> protection mechanism for plutonium-based materials is that in CO<jats:sub>2</jats:sub> molecule there occurs complete dissociation of CO<jats:sub>2</jats:sub> → C + O + O, then the dissociated C atom combines with O atom from O<jats:sub>2</jats:sub> dissociation and produces CO, which will inhibit the O<jats:sub>2</jats:sub> from further oxidizing Pu surface, and slow down the corrosion rate of plutonium-based materials.</jats:p>

<jats:p>We present a cluster mean-field study for ground-state phase diagram and many-body dynamics of spin-1 bosons confined in a two-chain Bose–Hubbard ladder (BHL). For unbiased BHL, we find superfluid (SF) phase and integer filling Mott insulator (IntMI) phase. For biased BHL, in addition to the SF and IntMI phases, there appears half-integer filling Mott insulator (HIntMI) phase. The phase transition between the SF and IntMI phases can be first order at a part of phase boundaries, while the phase transition between the SF and HIntMI phases is always second order. By tuning the bias energy, we report on the change of the nature of SF–MI phase transitions. Furthermore, we study the effect of the spin-dependent interaction on the many-body population dynamics. The spin-dependent interaction can lead to rich dynamical behaviors, but does not influence the particle transfer efficiency. Our results indicate a way to tune the nature of the SF–MI phase transition and open a new avenue to study the many-body dynamics of spinor bosons in optical lattices.</jats:p>

<jats:p>Atomistic simulations are carried out to investigate the nano-indentation of single crystal Cu and the sliding of the Cu–Zn alloy. As the contact zone is extended due to adhesive interaction between the contact atoms, the contact area on a nanoscale is redefined. A comparison of contact area and contact force between molecular dynamics (MD) and contact theory based on Greenwood–Williamson (GW) model is made. Lower roughness causes the adhesive interaction to weaken, showing the better consistency between the calculated results by MD and those from the theoretical model. The simulations of the sliding show that the substrate wear decreases with the mol% of Zn increasing, due to the fact that the diffusion movements of Zn atoms in substrate are blocked during the sliding because of the hexagonal close packed (hcp) structure of Zn.</jats:p>

<jats:p>Hydrogen, regarded as a promising energy carrier to alleviate the current energy crisis, can be generated from hydrogen evolution reaction (HER), whereas its efficiency is impeded by the activity of catalysts. Herein, effective strategies, such as strain and interfacial engineering, are imposed to tune the catalysis performance of novel two-dimensional (2D) phosphorus carbide (PC) layers using first-principle calculations. The findings show that P site in pristine monolayer PC (ML-PC) exhibits higher HER performance than C site. Intriguingly, constructing bilayer PC sheet (BL-PC) can change the coordinate configuration of P atom to form 3-coordination-P atom (3-co-P) and 4-coordination-P atom (4-co-P), and the original activity of 3-co-P site is higher than the 4-co-P site. When an external compressive strain is applied, the activity of the 4-co-P site is enhanced whereas the external strain can barely affect that of 3-co-P site. Interestingly, the graphene substrate enhances the overall activity of the BL-PC because the graphene substrate optimizes the Δ<jats:italic>G</jats:italic> <jats:sub>H*</jats:sub> value of 4-co-P site, although it can barely affect the HER activity of 3-co-P site and ML-PC. The desirable properties render 2D PC-based material promising candidates for HER catalysts and shed light on the wide utilization in electrocatalysis.</jats:p>