In this study, the electric field signatures of negative ground flashes pertinent to the Swedish thunderstorms were recorded simultaneously during the summer of 2014 using wide (up to 100 MHz) and narrow (at 3 MHz and 30 MHz as central frequencies) bandwidth antenna systems. The electric field signatures were recorded for a time duration of 250 ms. In the analysis, the whole flash was considered and a total of 98 flashes were chosen where electric field signatures of all wideband, 3 MHz and 30 MHz signals were present. It is observed that preliminary breakdown pulses are stronger radiators at 3 and 30 MHz compared to the return strokes. A comparison of our results with those of the previous studies obtained from different geographical regions clearly shows that the strength of preliminary breakdown pulses is higher in the temperate region (Sweden for instance) and is a function of latitude.

We investigated three novel 18-valence electron count (VEC) vanadium-based half-Heusler alloys, VYAl (Y = Ni, Pd, and Pt), for their structural, mechanical, electronic, and optical properties using density functional theory (DFT). The computation was carried out employing Vienna Ab-initio Simulation Package (VASP) and all three alloys have exhibited structural, chemical, mechanical, and thermodynamic stability. We obtained the lattice constants of 5.520, 5.800, and 5.820 Å for VNiAl, VPdAl, and VPtAl, respectively. The elastic parameters imply a ductile and hard nature of the system and exhibit anisotropic behavior. Electronic band characterization demonstrated that all three alloys are semiconductors with direct narrow gaps at the Γ-point which is crucial for photovoltaic applications. In addition to that, the high density of the band states near the Fermi level indicates a promising candidate for thermoelectric conversion. The influence of SOC interaction in the system generates a small shift in the bands. From the optical response, we infer that the studied compounds have exceptional light absorption and reflection quality, making them suitable for optoelectronics purposes.

MAX phase compounds have a unique blend of ceramic and metallic properties and have been established as promising materials for device applications. In the present work, we have investigated the structural, dynamical, mechanical, electronic, magnetic, and optical properties of Ti₂CdC and Ti₂SC MAX phase compounds using a density functional theory approach through the Vienna Ab initio Simulation Package. The structural, dynamical, and mechanical properties of both MAX phase compounds are studied and found to be stable. Additionally, the mechanical properties reveal that both compounds have hardness and a crystalline anisotropic, bond-stretching, and brittle nature. From the analysis of elastic anisotropy calculations, it is found that Ti₂CdC has metallic-like bonding, while Ti₂SC has covalent-like bonding. The electronic and magnetic properties of the Ti₂CdC and Ti₂SC compounds are determined, and it is found that they have metallic and non-magnetic properties for the generalized gradient approximation (GGA): Perdew–Burke–Ernzerh (PBE) functional, whereas they have metallic and magnetic properties for the GGA: PBE + U functional(U is Hubbard parameter). We have explored the optical properties of the considered materials and found that they have compelling interactions with electromagnetic radiation, notable values of absorption energy, that less transparency occurred at the lower energy region, and that they have high thermal properties. Based on the major findings of the above considered materials, Ti₂CdC and Ti₂SC can be used in the fields of optoelectronic devices, sensors, advanced photonic devices, infrared imaging, solar thermal collectors, thermal insulation, nuclear devices, and energy dissipation devices.

MAX phase compounds have numerous applications based on their dynamical, thermomechanical, electronic, magnetic, and optical properties. The performance of these compounds can be optimized by tailoring their composition, structure and processing methods to enhance their unique properties. In the present work, we explored the structural, dynamical, thermomechanical, electronic, magnetic, and optical properties of M₂AC (M = Ta, Sc; A = Al, Cd) (i.e. Sc₂AlC, Ta₂AlC & Ta₂CdC) MAX phase compounds using density functional theory (DFT) method with PBE and PBE + U functionals (U = 3eV for p-orbital, U = 5eV for d-orbital). From a thorough examination of the structural and dynamical properties of Sc₂AlC, Ta₂AlC, and Ta₂CdC compounds, they are found to be structurally and dynamically stable. We examine the thermal properties of these compounds by estimating their phonon velocities, Debye temperature, and various thermodynamic functions. These compounds have exhibited good thermal properties indicating their applicability in the thermoelectric devices. An examination of mechanical properties of these compounds was conducted by evaluating their elastic constants and modulus of rigidity. The results showed that they exhibit hardness and anisotropic properties. While Sc₂AlC & Ta₂CdC exhibit bond stretching and metallic-like bonding, Ta₂AlC exhibits bond bending and covalent-like bonding. On the other hand, Sc₂AlC & Ta₂AlC show brittle nature, whereas Ta₂CdC shows ductile nature. Electronic and magnetic properties of Sc₂AlC, Ta₂AlC, and Ta₂CdC compounds are investigated based on their band structure, density of states (DOS), and partial density of states (PDOS) plots, and all of them have shown metallic and non-magnetic properties. Upon examining the dielectric function, refractive index, reflection and absorption coefficients, extinction coefficient, and energy loss function of Sc₂AlC, Ta₂AlC, and Ta₂CdC are found to exhibit strong interaction with light, high shielding properties in the infrared region. Hence, Sc₂AlC, Ta₂AlC, and Ta₂CdC compounds can be used in the fields of thermoelectric, optoelectronic, material shielding, energy storage, and sensing devices.