Stacking Faults In Structures Research Articles

Modifying microscopic structures of MoS2 by high pressure and high temperature used in hydrogen evolution reaction

MoS2 is a classical catalyst for hydrogen evolution reaction (HER), but the performance is limited by poor electrical transport in c axis, and absent of active sites in (001) planes (basal planes). Simultaneously enhance the layer's interaction and activate the basal plane in MoS2 is urgent. In this work, a new sight of high pressure and high temperature (HPHT) was presented to modify the microscopic structures, and finally promoting the connection among the layers and activate the basal planes in bulk MoS2. It is found that high pressure generates shear between grains, and results stacking faults in structures. The stacking faults can enhance interaction between MoS2 sandwich layers, and reduce the charge transfer resistance. An intermediate state was captured, which exhibits distortions in structure at 3 GPa, 200 °C. The distortions cause longer or shorter Mo-S bonds, which introduce strains to activate the basal plane. Density functional theory (DFT) calculations show that the distortions can effective reduced the adsorption free energy of H* in MoS2 basal plane from 1.92 eV to 0.33 eV. So the activity of MoS2 was modified by HPHT, which indicates better activity than commercial MoS2. This work is not only significant to activate catalyst by HPHT, but also important to promote the functional materials.

Crystal structure and magnetic properties of the layered van der Waals compound VBr3

Single crystals of the layered, van der Waals compound $\mathrm{VB}{\mathrm{r}}_{3}$ were synthesized by a vapor transport technique, and characterized by single-crystal x-ray diffraction, temperature- and field-dependent magnetization, and temperature-dependent specific-heat measurements. $\mathrm{VB}{\mathrm{r}}_{3}$ has a honeycomb-based $\mathrm{Bi}{\mathrm{I}}_{3}$-type structure with space group $R\text{\ensuremath{-}}3$ (no. 148) at 100 K, analogous to the structure of other honeycomb trihalides. Structural stacking faults were observed as evidenced by the streaking of reflections along $c*$ in the diffraction data. $\mathrm{VB}{\mathrm{r}}_{3}$ goes through a structural phase transition at 90.4 K and a subsequent antiferromagnetic phase transition at 26.5 K, below which the magnetic moments are primarily aligned along the $c$ axis.

On the characterization and origin of the dislocations associated with the two way memory effect in CuZnAl thermoelastic alloys—II. The model for the formation of dislocations

We propose a model for the formation of dislocations produced by the martensitic transformation of β phases into 18R (or 9R) structures in thermoelastic alloys. The model is based on the combination of fault vectors associated with the structural stacking faults always present in 18R or 9R martensites. This explains the type and geometry of the dislocations observed in the β 1 phase after the reverse transformation.