Fazel Shojaei

In recent decades, materials with nonlinear optical properties have become an important research area in both theoretical and experimental studies due to their widespread applications in advanced technologies. Therefore, designing materials with nonlinear optical properties is essential to meet the needs of various technologies. Additionally, following the discovery of graphene, significant efforts have been devoted to the synthesis and design of two-dimensional nanomaterials. In this context, bulk polycrystalline NaSnAs samples have been synthesized, which have a germanium-like hexagonal structure and consist of SnAs sheets separated by Na atoms. In this regard, in the present work, systematic theoretical calculations are performed to study the possible formation of finite-size nanowire assemblies by stacking B14 or B14M (M= Fe, Co) building blocks. The size evolution of structure, electronic, static, and dynamic nonlinear optical (NLO) properties of (B14)n, (B14Fe)n, and (B14Co)n with n=1-6 are investigated. Although, the drum-shaped structure of the building blocks is retained in most cases, however, in larger sizes of assemblies the small expansion of building blocks at the middle and the compression at the terminals are observed. Our results highlight that the energy gap of boron nanowire assemblies can be finely tuned by altering their length. This is also inspiring for the modulation of the first hyperpolarizability by varying the number of stacked units. Among all the examined systems, the highest hyperpolarizability (βtot = 1.35 × 105 a.u.) is observed for (B14Fe)6 owing to the reduced energy gap and increased charge transfer.