Density-functional-studying of oP8–, tI16–, and tP4–B2CO physical properties under pressure

Investigation of half metallic properties of Tl2Mo(Cl/Br)6 double perovskites for spintronic devices

The manipulation of electronic device characteristics through electron spin represents a burgeoning frontier in technological advancement. Investigation of magnetic and transport attributes of the Tl2Mo(Cl/Br)6 double perovskite was performed using Wien2k and BoltzTraP code. When the energy states between ferromagnetic and antiferromagnetic conditions are compared, it is evident that the ferromagnetic state exhibits lower energy levels. Overcoming stability challenges within the ferromagnetic state is achieved through the manipulation of negative ΔHf within the cubic state. The analysis of the half metallicity character involves an analysis of band structure (BS) and DOS, elucidating its mechanism through PDOS using double exchange model p-d hybridization. The verification of 100% spin polarization is confirmed through factors such as spin polarization and the integer value of the total magnetic moment. Furthermore, the thermoelectric response, as indicated by the ratios of thermal-electrical conductivity and ZT, underscores the promising applications of these compounds in thermoelectric device applications.

A New BCN Compound with Monoclinic Symmetry: First-Principle Calculations

In this study, we predicted and investigated a new light-element compound B-C-N in Pm phase, denoted as Pm-BCN, using density functional theory. Pm-BCN is mechanically, dynamically, and thermodynamically stable. The elastic moduli of Pm-BCN are larger than those of other B-C-N and light-element compounds, such as P2₁3 BN, B₂C₃, P4/m BN, Pnc2 BN, and dz4 BN. By studying the mechanical anisotropy of elastic moduli, we proved that Pm-BCN is a mechanically anisotropic material. In addition, the shear anisotropy factors A₂ and A_Ba of Pm-BCN are smaller than those of the seven B-C-N compounds mentioned in this paper. Pm-BCN is a semiconductor material with an indirect and wide band gap, suggesting that Pm-BCN can be applied in microelectronic devices.

Novel III-V Nitride Polymorphs in the P42/mnm and Pbca Phases

In this work, the elastic anisotropy, mechanical stability, and electronic properties for P4₂/mnm XN (XN = BN, AlN, GaN, and InN) and Pbca XN are researched based on density functional theory. Here, the XN in the P4₂/mnm and Pbca phases have a mechanic stability and dynamic stability. Compared with the Pnma phase and Pm-3n phase, the P4₂/mnm and Pbca phases have greater values of bulk modulus and shear modulus. The ratio of the bulk modulus (B), shear modulus (G), and Poisson’s ratio (v) of XN in the P4₂/mnm and Pbca phases are smaller than those for Pnma XN and Pm-3n XN, and larger than those for c-XN, indicating that Pnma XN and Pm-3n XN are more ductile than P4₂/mnm XN and Pbca XN, and that c-XN is more brittle than P4₂/mnm XN and Pbca XN. In addition, in the Pbca phases, XN can be considered a semiconductor material, while in the P4₂/mnm phase, GaN and InN have direct band-gap, and BN and AlN are indirect wide band gap materials. The novel III-V nitride polymorphs in the P4₂/mnm and Pbca phases may have great potential for application in visible light detectors, ultraviolet detectors, infrared detectors, and light-emitting diodes.

Optical, Electronic Properties and Anisotropy in Mechanical Properties of "X" Type Carbon Allotropes

Based on first-principle calculations, the mechanical anisotropy and the electronic and optical properties of seven kinds of carbon materials are investigated in this work. These seven materials have similar structures: they all have X-type structures, with carbon atoms or carbon clusters at the center and stacking towards the space. A calculation of anisotropy shows that the order of elastic anisotropy in terms of the shear modulus, Young's modulus and Poisson's ratio of these seven carbon materials with similar structure is diamond < supercubane < T carbon < Y carbon < TY carbon < cubane-diyne < cubane-yne. As these seven carbon materials exhibit cubic symmetry, Young's modulus has the same anisotropy in some major planes, so the order of elastic anisotropy in the Young's modulus of these seven main planes is (111) plane < (001) plane = (010) plane = (100) plane < (011) plane = (110) plane = (101) plane. It is also due to the fact that their crystal structure has cubic symmetry that the elastic anisotropy in the shear modulus and the Poisson's ratio of these seven carbon materials on the seven major planes are the same. Among the three propagation directions of [100], [110], and [111], the [110] propagation direction's anisotropic ratio of the sound velocity of TY carbon is the largest, while the anisotropic ratio of the sound velocity of cubane-diyne on the [100] propagation direction is the smallest. In addition, not surprisingly, the diamond has the largest Debye temperature, while the TY carbon has the smallest Debye temperature. Finally, TY carbon, T carbon and cubane-diyne are also potential semiconductor materials for photoelectric applications owing to their higher or similar absorption coefficients to GaAs in the visible region.