Relaxor-ferroelectrics are fascinating and useful materials, but the mechanism of relaxor-ferroelectricity has been puzzling the scientific community for more than 65 years. Here, a theory of relaxor-ferroelectricity is presented based on 3-dimensional-extended-random-site-Ising-model along with Glauber-dynamics of pseudospins. We propose a new mean-field of pseudospin-strings to solve this kinetic model. The theoretical results show that, with decreasing pseudospin concentration, there are evolutions from normal-ferroelectrics to relaxor-ferroelectrics to paraelectrics, especially indicating by the crossovers from, (a) the sharp to diffuse change at the phase-transition temperature to disappearance in the whole temperature range of order-parameter, and (b) the power-law to Vogel-Fulcher-law to Arrhenius-relation of the average relaxation time. Particularly, the calculated local-order-parameter of the relaxor-ferroelectrics gives the polar-nano-regions appearing far above the diffuse-phase-transition and shows the quasi-fractal characteristic near and below the transition temperature. We also provide a new mechanism of Burns-transformation which stems from not only the polar-nano-regions but also the correlation-function between pseudospins, and put forward a definition of the canonical relaxor-ferroelectrics. The theory accounts for the main facts of relaxor-ferroelectricity, and in addition gives a good quantitative agreement with the experimental results of the order-parameter, specific-heat, high-frequency permittivity, and Burns-transformation of lead magnesium niobate, the canonical relaxor-ferroelectric.

By the study of a series of molecular liquids of fragilities covering almost the entire known range by the mechanical spectroscopy of quantitatively monitoring the healing of stress-induced microcracks recently developed by W. H. Wu et al. [Appl. Phys. Lett. 92, 011918 (2008)], we show that the cracking healing temperature coincides with the onset glass temperature Tg, quite independent of the liquid fragility. Another interesting observation is that the major part of the modulus recovery occurs below Tg. Thus, our study establishes an additional approach to the study of the glass dynamics and glass transition which lends itself to a variety of potential applications.

A mechanical spectroscopy method of quantitatively monitoring the healing of stress-induced microcracks in small glass samples is described. Whereas the cracks are generated catastrophically at some unpredictable interval below the glass temperature $T_g$ the healing process proves to be highly reproducible and a characteristic temperature for the crack healing process, the temperature of maximum healing rate $T_{\mathrm{ch}}$ coincides with $T_g$ .

The single-layer MoS₂ is a highly sought-after semiconductor material in the field of photoelectric performance due to its exceptional electron mobility and narrow bandgap. However, its photocatalytic efficiency is hindered by the rapid recombination rate of internal photogenerated electron–hole pairs. Currently, the construction of heterojunctions has been demonstrated to effectively mitigate the recombination rate of photogenerated electron–hole pairs. Therefore, this paper employs the first principles method to calculate and analyze the four heterojunctions formed by MoS₂/WSe₂, MoS₂/MoSe₂, MoS₂/AlN, and MoS₂/ZnO. The study demonstrates that the four heterojunctions exhibit structural stability. The construction of heterojunctions, as compared to a monolayer MoS₂, leads to a reduction in the band gap, thereby lowering the electron transition barrier and enhancing the light absorption capacity of the materials. The four systems exhibit II-type heterojunction. Therefore, the construction of heterojunctions can effectively enhance the optical properties of these systems. By forming heterojunctions MoS₂/WSe₂ and MoS₂/MoSe₂, the absorption coefficient in the visible light region is significantly increased, resulting in a greater ability to respond to light compared to that of MoS₂/ZnO and MoS₂/AlN. Consequently, MoS₂-based heterojunctions incorporating chalcogenide components WSe₂ and MoSe₂, respectively, exhibit superior catalytic activity compared to MoS₂ heterojunctions incorporating non-chalcogenide components ZnO and AlN, respectively. The absorption spectrum analysis reveals that MoS₂/MoSe₂ exhibits the highest light responsivity among all investigated systems, indicating its superior photoelectric performance.

For ternary borates containing BO₃planar triangles only, α-/β-TM₃(BO₃)₂(TM = Zn, Cd), Cd₂B₂O₅, and M₃(BO₃)₂(M = Hg, Mg, Ca, Sr), a large optical permittivity Δεmakes a positive contribution to the birefringence Δn.

The energy band structure, density of states, and optical properties of monolayers of MoS₂ doped with alkaline earth metals (Be/Mg/Ca/Sr/Ba) are systematically studied based on first principles. The results indicate that all the doped systems have a great potential to be formed and structurally stable. In comparison to monolayer MoS₂, doping alkaline earth metals results in lattice distortions in the doped system. Therefore, the recombination of photogenerated hole–electron pairs is suppressed effectively. Simultaneously, the introduction of dopants reduces the band gap of the systems while creating impurity levels. Hence, the likelihood of electron transfer from the valence to the conduction band is enhanced, which means a reduction in the energy required for such a transfer. Moreover, doping monolayer MoS₂ with alkaline earth metals increases the static dielectric constant and enhances its polarizability. Notably, the Sr–MoS₂ system exhibits the highest value of static permittivity, demonstrating the strongest polarization capability. The doped systems exhibit a red-shifted absorption spectrum in the low-energy region. Consequently, the Be/Mg/Ca–MoS₂ systems demonstrate superior visible absorption properties and a favorable band gap, indicating their potential as photo-catalysts for water splitting.