Black phosphorus (BP), a new two-dimensional material, has been the focus of scientists’ attention. BP nanotubes have potential in the field of optoelectronics due to their low-dimensional effects. In this work, the bending strain energy, electronic structure, and optical properties of BP nanotubes were investigated by using the first-principles method based on density functional theory. The results show that these properties are closely related to the rolling direction and radius of the BP nanotube. All the calculated BP nanotube properties show direct bandgaps, and the BP nanotubes with the same rolling direction express a monotone increasing trend in the value of bandgap with a decrease in radius, which is a stacking effect of the compression strain on the inner atoms and the tension strain on the outer atoms. The bending strain energy of the zigzag phosphorene nanotubes (zPNTs) is higher than that of armchair phosphorene nanotubes (aPNT) with the same radius of curvature due to the anisotropy of the BP’s structure. The imaginary part of the dielectric function, the absorption range, reflectivity, and the imaginary part of the refractive index of aPNTs have a wider range than those of zPNTs, with higher values overall. As a result, tunable BP nanotubes are suitable for optoelectronic devices, such as lasers and diodes, which function in the infrared and ultra-violet regions, and for solar cells and photocatalysis.

The current work investigates a novel three-dimensional boron nitride called bulk B₄N₄ and its corresponding two-dimensional monolayer B₄N₄ based on the first-principles of density functional theory. The phonon spectra prove that bulk B₄N₄ and monolayer B₄N₄ are dynamically stable. The molecular dynamics simulations verify that bulk B₄N₄ and monolayer B₄N₄ have excellent thermal stability of withstanding temperature up to 1000 K. The calculated elastic constants state that bulk B₄N₄ and monolayer B₄N₄ are mechanically stable, and bulk B₄N₄ has strong anisotropy. The theoretically obtained electronic structures reveal that bulk B₄N₄ is an indirect band-gap semiconductor with a band gap of 5.4 eV, while monolayer B₄N₄ has a direct band gap of 6.1 eV. The valence band maximum is mainly contributed from B-2p and N-2p orbits, and the conduction band minimum mainly derives from B-2p orbits. The electron transitions from occupied N-2p states to empty B-2p states play important roles in the dielectric functions of bulk B₄N₄ and monolayer B₄N₄. The newly proposed monolayer B₄N₄ is a potential candidate for designing optoelectronic devices such as transparent electrodes due to its high transmissivity.

The flow behavior of an Al-Cu-Li-Mg-Ag alloy was studied by thermal simulation tests at deformation temperatures between 350 °C and 470 °C and strain rates between 0.01–10 s⁻¹. The microstructures of the deformed materials were characterized by electron backscattered diffraction. Constitutive equations were developed after considering compensation for strains. The processing maps were established and the optimum processing window was identified. The experimental data and predicted values of flow stresses were in a good agreement with each other. The influence of deformation temperature and strain rates on the microstructure were discussed. The relationship between the recrystallization mechanism and the Zener–Hollomon parameter was investigated as well.

Using the density functional theory prediction, we investigate the structural, elastic, electronic, optical, and vibrational properties of B- and X-dependent double perovskites Rb₂BCl₆ (B = Ti, Se, Pd) and Rb₂PdX₆ (X = F, Cl, Br, I) in this work. They are indirect bandgap semiconductors. For Rb₂BCl₆, the top valence bands are dominated by Cl-3p states and the bottom conduction bands by Ti-4d/Se-5p/Pd-5d states. For Rb₂PdX₆, the top valance bands are formed by X-p (F-2p, Cl-3p, Br-4p, and I-5p) states, and the bottom conduction bands are mainly composed of Pd-5d states. The high values of imaginary dielectric functions, high absorption coefficients, and low reflection coefficients indicate that Rb₂BCl₆ (B = Ti, Se, Pd) and Rb₂PdX₆ (X = F, Cl, Br, I) double perovskites are potential lead-free photoelectric materials. In addition, Rb₂PdX₆ (X = Br, I) double perovskites have the potential to be used in photovoltaic applications as they have broad optical absorption in the visible light range and dynamic stability under 400 K. The lattice vibrations of Rb₂PdF₆, examined as an example, show that the high-frequency vibration modes (T_1u, T_2g, E_g, and A_1g) are derived from PdF₆²⁻ clusters, while the low-frequency vibration modes (T_2g and T_1u) are contributed by Rb atoms.