Computational modeling and characterization of X-Bi (X = B, Al, Ga, In) compounds: Prospective optoelectronic materials for infrared/near infra applications

III-V compounds containing heavy Bi anion are distinguished from remaining III-V family in terms of their narrower electronic energy gap and potential application for infrared/near infra devices. In the present work, modeling of X-Bi (X = B, Al, Ga and In) compounds and the investigations pertaining to their physical properties were carried out using density functional theory (DFT) based full-potential linearized augmented plane wave plus local orbital, FP-L(APW + lo) approach within various functional of the exchange correlation potentials. The calculated total energies of X-Bi in various geometries reveal that zinc blende phase is the stable ground state structure of BBi, AlBi and GaBi. However, InBi adapts PbO phase at ground state. It was also found that BBi exhibit an electronic structure with an indirect energy gap. However, AlBi, GaBi and InBi are semi-metallic with a narrower or zero band gap. The calculation of the optical properties show that among X-Bi compounds, BBi was found to exhibit higher absorption coefficient values, lower reflectivity and refractive index, enlightening their potential for infrared/near infra devices and other optoelectronic applications as well

Kinetics and Thermochemistry of the Reaction Si(CH₃)₃ + HBr ⇋ Si(CH₃)₃H + Br: Determination of the (CH₃)₃Si-H Bond Energy

Article on kinetics and thermochemistry of the reaction Si(CH₃)₃ + HBr ⇋ Si(CH₃)₃H + Br and determination of the (CH₃)₃Si-H bond energy

Electronic structure and mechanical properties of ternary ZrTaN alloys studied by ab initio calculations and thin-film growth experiments

The structure, phase stability, and mechanical properties of ternary alloys of the Zr-Ta-N system are investigated by combining thin-film growth and ab initio calculations. Zr1-xTaxN films with 0≤x≤1 were deposited by reactive magnetron cosputtering in Ar+N2 plasma discharge and their structural properties characterized by x-ray diffraction. We considered both ordered and disordered alloys, using supercells and special quasirandom structure approaches, to account for different possible metal atom distributions on the cation sublattice. Density functional theory within the generalized gradient approximation was employed to calculate the electronic structure as well as predict the evolution of the lattice parameter and key mechanical properties, including single-crystal elastic constants and polycrystalline elastic moduli, of ternary Zr1-xTaxN compounds with cubic rocksalt structure. These calculated values are compared with experimental data from thin-film measurements using Brillouin light scattering and nanoindentation tests. We also study the validity of Vegard's empirical rule and the effect of growth-dependent stresses on the lattice parameter. The thermal stability of these Zr1-xTaxN films is also studied, based on their structural and mechanical response upon vacuum annealing at 850°C for 3 h. Our findings demonstrate that Zr1-xTaxN alloys with Ta fraction 0.51≤x≤0.78 exhibit enhanced toughness, while retaining high hardness ∼30 GPa, as a result of increased valence electron concentration and phase stability tuning. Calculations performed for disordered or ordered structures both lead to the same conclusion regarding the mechanical behavior of these nitride alloys, in agreement with recent literature findings [H. Kindlund, D. G. Sangiovanni, L. Martinez-de-Olcoz, J. Lu, J. Jensen, J. Birch, I. Petrov, J. E. Greene, V. Chirita, and L. Hultman, APL Materials 1, 042104 (2013)10.1063/1.4822440]