The adsorption and interaction mechanisms of gaseous molecules on ZnO surfaces have received considerable attention because of their technological applications in gas sensing. The adsorption behavior of NH₃ and NO₂ molecules on undoped and Sn-doped ZnO (101) surfaces was investigated using density functional theory. The current findings revealed that both molecules adsorb via chemisorption rather than physisorption, with all the adsorption energy values found to be negative. The calculated adsorption energy revealed that the adsorption of the NH₃ molecule on the bare ZnO surface is more energetically favorable than the adsorption of the NO₂ molecule. However, a stable adsorption configuration was discovered for the NO₂ molecule on the surface of the Sn-doped ZnO surface. Furthermore, the adsorption on the undoped surface increased the work function, while the adsorption on the doped surface decreased. The charge density redistribution showed charge accumulation and depletion on both adsorbent and adsorbate. In addition, the density of states and band structures were studied to investigate the electronic behavior of NH₃ and NO₂ molecules adsorbed on undoped and Sn-doped ZnO (101) surfaces.

Shape memory alloys find application as sensors, microcontrollers or actuators. The TiPt binary system, a potential high temperature shape memory alloy due to its high transformation temperature of approximately 1000°C, displays negligible work output. This makes it unsuitable for actuator applications where work output is a prerequisite. A necessary condition for sufficient work output is for the alloy to display a critical stress for slip in austenite phase greater than detwinning stress of martensite phase. Solid solution strengthening, work hardening and precipitation hardening are possible mechanisms to improve work output. An indirect consequence of solid solution strengthening is altering of the crystal structure and the transformation temperature. This study evaluates the effect of partial substitution of Pt with V to form ternary Ti₅₀Pt_43.75V_6.25 (at.%) on the above-mentioned properties. Phase analysis and identification was done using scanning electron microscopy with energy-dispersive X-Ray spectroscopy and X-Ray diffraction. The transformation temperatures were studied by differential scanning calorimetry. Results show a three-phase microstructure with B19 Ti₅₀(PtV)₅₀ martensite as the major phase. The transformation temperature reduced with addition of vanadium in agreement with the predicted results from first-principles approach. However, the experimentally observed B19 structure did not agree with first-principles studies at 0K where B19' was the predicted stable phase.

The demand for shape memory alloys for high temperatures have increased in recent years and TiPt alloys are promising candidates. The martensitic transformation temperature of TiPt is higher with the value of approximately 1300 K as compared to the commercialised TiNi which transforms at 300 K. Titanium-based SMAs have been widely used in the fields of engineering and medicine due to their shape memory effect (SME) and super-plasticity which are displayed in martensitic transformations. Some of the applications include actuators and medical stents. Previous studies showed that the alloy is mechanically unstable with the negative C' modulus at 0 K. In this work, supercell approach is used to substitute Pt with vanadium on the B2 TiPt structure and evaluate the mechanical stability of the structures. The equilibrium lattice parameters, elastic properties and the phonon dispersions were calculated to investigate the stability of the Ti₅₀Pt_50-XV_X. Interestingly the vanadium addition was found to be stabilising the TiPt with all the C_ij's being positive.

The study on the Ti-based materials and its application has been the interest of many research industries. These alloys are known to have an ordered B2 phase at high temperatures and transform to a stable low B19 martensitic phase. First principle approach has been used to study L1₀, B32, B2 and B19 Ti₅₀Al₅₀ alloys and the results compared well with the available experimental data. The equilibrium lattice constants are in good agreement with the experimental values (within 3% agreement). Furthermore, the elastic constants of these alloys are calculated, and revealed stability for L1₀ and B19 structures, while B2 and B32 gave C′<0 (condition of instability).

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First-principles density functional theory approach was employed to investigate the martensitic temperature of the equiatomic TiPt, TiZr and TiTa shape memory alloys. Firstly, their structural, thermodynamic, elastic and phonon dispersion have been deduced to mimic the relative stabilities. These alloys have potential to operate as high-temperature shape memory alloys since they possess a reversible B2 to B19 martensitic transformation. It was found that the lattice parameters are in good agreement with the experimental results to within 5%. Furthermore, the TiPt structure is thermodynamically stable displaying lowest heats of formation, while TiZr and TiTa are not. Our results show that the B2 phases of these binary alloys are vibrational unstable due to the presence of soft modes along high symmetry direction on the phonon dispersion curves. TiTa alloy is mechanically stable (C' > 0), which may be used to develop future high-temperature alloys.