On the electronic and geometric structures of armchair GeC nanotubes: a hybrid density functional study

Abstract

Ab initio calculations within the framework of hybrid density functional theory and the finite cluster approximation have been performed for the electronic and geometric structures of three different types of armchair germanium carbide nanotube, from (3, 3) to (11, 11). Full geometry and spin optimizations with unrestricted symmetry have been performed. Physically pertinent quantities of interest such as the cohesive energies, band gaps, radial buckling, density of states, dipole moments, and Mulliken charge distributions have been investigated in detail for all nanotubes. For type I nanotubes, the largest cohesive energy obtained is 4.092 eV/atom, whereas for type II and type III nanotubes, the values are 3.987 eV/atom and 3.968 eV/atom, respectively. For optimized type I nanotubes, Ge atoms moved toward the tube axis and C atoms moved in the opposite direction after relaxation, opposite to the trends observed in types II and III. The band gaps for type I nanotubes are larger than the bulk 3C-GeC gap, varying between 2.666 and 3.016 eV, while type II and type III nanotubes have significantly lower band gaps, with all nanotubes being semiconducting in nature. Mulliken charge analysis indicates primarily ionic behavior for type I GeC nanotubes and a mixed ionic with covalent behavior for the other two types. None of the tubes appear to be magnetic. Applications in the field of nano-optoelectronic devices, molecular electronics, and band gap engineering are envisioned for GeC nanotubes.

Electronic properties of finite‐length silicon carbide nanotubes

“…No differences of the Mulliken charge density as a function of length could be observed. As ionicity is believed to be responsible for the increasing localization of the electronic states [19], we observed higher localized HOMO and LUMO for larger diameter SiCNTs. However, orbitals localization also increased with length.…”

“…(5,5), rises. This means that in general among armchair SiCNTs, the (2,2) are comparatively the least stable, because small diameter nanotubes have stronger curvature causing strain [19]. In fact, the (2,2) SiCNT has the broadest Si-C bond length distribution (1.76-1.87 Å) compared to the larger diameter ones (see Table 1), because the bonds expands to minimize the strain energy [19].…”

Excitonic effects in GeC hybrid: Many-body Green's function calculations

“…Other applications of GeC thin films for design and preparation of durable multilayer coatings of infrared (IR) windows were reported in [13]. GeC nanotubes with an average diameter of 15 − 100nm were synthesized using MOCVD techniques as promising candidates for complex nano-based applications in wide band gap nanooptoelectronic devices and hydrogen storage [14,15]. In 2D, germanene/graphene hybrid is a honeycomb lattice where germanium and carbon atoms are arranged with sp 2 hybridization [16].…”

Tuned electronic, optical and mechanical properties of pristine and hetero nanotubes of group IV elements (C, Si and Ge)

“…SiC nanotubes are also being successfully synthesized in various laboratories using various methods [26,27] and it has also been suggested that SiC nanotubes can be a potential candidate for hydrogen storage [28]. Rathi and Ray [29] studied the electronic and geometric structures of hydrogenated GeC nanotubes and found the nanotubes to be semiconducting.…”