Specific features of the three high-symmetry domains of the FeO/Au moiré superstructure (surface electrostatic potential, work function, local film rumpling, interface distance and charge transfer) are identified thanks to VASP-DFT calculations.

In this study, we present a combined experimental and theoretical study of point defects in MoS₂ monolayers supported on Au(111). By tuning the experimental conditions, we achieved selective defect formation, paving the way for advanced defect engineering. Density functional theory (DFT) simulations were performed to model both the perfect Moiré superstructure and a variety of defect configurations. This allowed us to precisely identify the experimentally created single- and multiatom vacancies, interpret their contrast in scanning tunneling microscopy (STM), and characterize their electronic properties and effects on the valence band (VB). Our results show that tuning the kinetics of ion bombardment and the chemical environment during annealing treatments can produce different combinations of simple and complex defects. Additionally, we find that the Moiré modulation has minimal impact on the geometric and electronic properties of the surface, suggesting that the defect-engineered MoS₂/Au surface could serve as a rather general model system to further investigate the electronic and catalytic properties of MoS₂-based nanomaterials.

DFT was applied to study the LiIn surfaces' formation and structural stability in interfaces with β-Li ₃ PS ₄ . The stable interfaces established with the β-Li ₃ PS ₄ featured favorable adhesion energy, low strain energy, and little reconstruction.

The half Heusler TiNiSn compound is a model system for understanding the relationship among structural, electronic, microstructural and thermoelectric properties. However, the role of defects that deviate from the ideal crystal structure is far from being fully described. In this work, TiNi_1+x Sn alloys (x = 0, 0.03, 0.06, 0.12) were synthesized by arc melting elemental metals and annealed to achieve equilibrium conditions. Experimental values of the Seebeck coefficient and electrical resistivity, obtained from this work and from the literature, scale with the measured carrier concentration, due to different amounts of secondary phases and interstitial nickel. Density functional theory calculations showed that the presence of both interstitial Ni defects and composition conserving defects narrows the band gap with respect to the defect free structure, affecting the transport properties. Accordingly, results of experimental investigations have been explained confirming that interstitial Ni defects, as well as secondary phases, promote a metallic behavior, raising the electrical conductivity and lowering the absolute values of the Seebeck coefficient.

In the wide group of thermoelectric compounds, the half-Heusler ZrNiSn alloy is one of the most promising materials thanks to its thermal stability and narrow band gap, which open it to the possibility of mid-temperature applications. A large variety of defects and doping can be introduced in the ZrNiSn crystalline structure, thus allowing researchers to tune the electronic band structure and enhance the thermoelectric performance. Within this picture, theoretical studies of the electronic properties of perfect and defective ZrNiSn structures can help with the comprehension of the relation between the topology of defects and the thermoelectric features. In this work, a half-Heusler ZrNiSn alloy is studied using different defective models by means of an accurate Density Functional Theory supercell approach. In particular, we decided to model the most common defects related to Ni, which are certainly present in the experimental samples, i.e., interstitial and antisite Ni and a substitutional defect consisting of the replacement of Sn with Sb atoms using concentrations of 3% and 6%. First of all, a comprehensive characterization of the one-electron properties is performed in order to gain deeper insight into the relationship between structural, topological and electronic properties. Then, the effects of the modeled defects on the band structure are analyzed, with particular attention paid to the region between the valence and the conduction bands, where the defective models introduce in-gap states with respect to the perfect ZrNiSn crystal. Finally, the electronic transport properties of perfect and defective structures are computed using semi-classical approximation in the framework of the Boltzmann transport theory as implemented in the Crystal code. The dependence obtained of the Seebeck coefficient and the power factor on the temperature and the carrier concentration shows reasonable agreement with respect to the experimental counterpart, allowing possible rationalization of the effect of the modeled defects on the thermoelectric performance of the synthesized samples. As a general conclusion, defect-free ZrNiSn crystal appears to be the best candidate for thermoelectric applications when compared to interstitial and antisite Ni defective models, and substitutional defects of Sn with Sb atoms (using concentrations of 3% and 6%) do not appreciably improve electronic transport properties.