arXiv subjects

Michal Novotný

Publications and source records attributed to Michal Novotný.

2 recordsLinked to original sources

arXiv2024

The effect of mixed termination composition in Sc, Ti, and V-based MXenes

In this study, we investigate the effect of mixed surface terminations (F, O, OH) on the properties of M$_{2}$C MXenes (M = Sc, Ti, V). We explore how different compositions and patterns of terminal groups affect the stability and electronic properties of these 2D materials. The bond dissociation energies and cohesion energies show a clear preference for F-terminations in Sc$_{2}$C, while Ti- and V-based MXenes prefer O-terminations. The data indicates that terminal groups on opposite sides of the MXene have little to no influence on each other's electronic structure, allowing for independent chemical environments on each side. Semiconducting forms of studied MXenes (Sc$_{2}$CF$_{2}$, Sc$_{2}$C(OH)$_{2}$ and Ti$_{2}$CO$_{2}$) showed very high sensitivity to conduction-inducing terminations (O, O, and F, respectively) with even minuscule amounts ($\approx$1%) causing the materials to become conductive. This high sensitivity of the band gap to surface terminations may offer an explanation for the challenges in synthesizing semiconducting forms of MXenes.

cond-mat.mtrl-sci↗

arXiv2021

Lattice dynamics in the conformational environment of multilayered hexagonal boron nitride (h-BN) conveys to peculiar infrared optical responses

Stacking mismatches in hexagonal boron nitride (h-BN) nanostructures affect their photonic, mechanical, and thermal properties. To access information about the stacked configuration of layered ensembles, highly sophisticated techniques like X-ray photoemission spectroscopy or electron microscopy are necessary. Here, instead, by taking advantage of the geometrical and chemical nature of h-BN, we show how simple structural models, based on shortened interplanar distances, can produce effective charge densities. Accounting these in the non-analytical part of the lattice dynamical description makes it possible to access information about the composition of differently stacked variants in experimental samples characterized by infrared spectroscopy. The results are obtained by density functional theory and confirmed by various functionals and pseudopotential approximations. Even though the method is shown on h-BN, the conclusions are more general and show how effective dielectric models can be considered as valuable theoretical pathways for the vibrational structure of any layered material.

cond-mat.mtrl-sci↗