arXiv subjects

Junga Ryou

Publications and source records attributed to Junga Ryou.

4 recordsLinked to original sources

arXiv2020

Edge-functionalization of armchair graphene nanoribbons with pentagonal-hexagonal edge structures

Using density functional theory calculations, we have studied the edge-functionalization of armchair graphene nanoribbons (AGNRs) with pentagonal-hexagonal edge structures. While the AGNRs with pentagonal-hexagonal edge structures (labeled (5,6)-AGNRs) are metallic, the edge-functionalized (5,6)-AGNRs with substitutional atoms opens a band gap. We find that the band structures of edge-functionalized (5,6)-N-AGNRs by substitution resemble those of defect-free (N-1)-AGNR at the {\Gamma} point, whereas those at the X point show the original ones of the defect-free N-AGNR. The overall electronic structures of edge-functionalized (5,6)-AGNRs depend on the number of electrons, supplied by substitutional atoms, at the edges of functionalized (5,6)-AGNRs.

cond-mat.mes-hall↗

arXiv2015

Electronic properties of bilayer graphenes strongly coupled to interlayer stacking and an external electric field

Bilayer graphene (BLG) with a tunable bandgap appears interesting as an alternative to graphene for practical applications, thus its transport properties are being actively pursued. Using density functional theory and perturbation analysis, we investigated, under an external electric field, the electronic properties of BLGs in various stackings relevant to recently observed complex structures. We established the first phase diagram summarizing the stacking-dependent gap openings of BLGs for a given field. We further identified high-density midgap states, localized on grain boundaries, even under a strong field, which can considerably reduce overall transport gap.

cond-mat.mtrl-sci↗

arXiv2011

Origins of dihydrogen binding to metal-inserted porphyrins: electric polarization and Kubas interaction

Using density functional theory calculations, we have investigated the interactions between hydrogen molecules and metalloporphyrins. A metal atom such as Ca or Ti is introduced for incorporation in the central N$_4$ cavity. Within local density approximation (generalized gradient approximation), we find that the average binding energy of H$_2$ to the Ca atom is about 0.25 (0.1) eV/H$_2$ up to four H$_2$ molecules, whereas that to the Ti atom is about 0.6 (0.3) eV per H$_2$ up to two H$_2$. Our analysis of orbital hybridization between the inserted metal atom and molecular hydrogen shows that H$_2$ binds weakly to Ca-porphyrin through a weak electric polarization in dihydrogen, but is strongly hybridized with Ti-porphyrin through the Kubas interaction. The presence of $d$ orbitals in Ti may explain the difference in the interaction types.

cond-mat.mes-hall↗

arXiv2009

Hydrogen adsorption on hexagonal silicon nanotubes

We present a first-principles study of geometrical structure and energetics of hydrogen adsorbed on hexagonal single-walled silicon nanotubes (SiNTs). The adsorption behaviors of hydrogen molecules in SiNTs are investigated. The binding energies for the most stable physisorbed configurations are calculated to be less than 0.1 eV. The energy barriers are also investigated for dissociation of H2 molecules. Finally, we consider encapsulation of H2 molecules in SiNTs. The possibility of SiNTs as hydrogen storage materials is discussed.

cond-mat.mtrl-sci↗