Electronic and optical properties of novel carbon allotropes

Abstract

The phonon properties, electronic structures and optical properties of novel carbon allotropes, such as monolayer penta-graphene (PG), double-layer PG and T12-carbon, were explored by means of first-principles calculations. Results of phonon calculations demonstrate that these exotic carbon allotropes are dynamically stable. In addition, the bulk T12 phase is an indirect-gap semiconductor having a bandgap of ~4.89 eV. Whereas the bulk material transforms to a 2D phase, the monolayer and double-layer PG become quasi-direct gap semiconductors with smaller band gaps of ~2.64 eV and ~3.27eV, respectively. Furthermore, the partial charge density analysis indicates that the 2D phases retain part of the electronic characteristics of the T12 phase. The linear photon energy-dependent dielectric functions and related optical properties including refractive index, extinction coefficient, absorption spectrum, reflectivity, and energy loss spectrum were also computed and discussed. The structural estimation obtained as well as other findings are in agreement with existing theoretical data. The calculated results are beneficial to the practical applications of these exotic carbon allotropes in optoelectronics and electronics.

Boron‐ and nitrogen‐doped penta‐graphene as a promising material for hydrogen storage: A computational study

“…The dissociation process of H 2 is ended up with two hydrogen atoms on the cc 1 site (bc 1 and nc 1 sites for B‐ and N‐doped PG), which is chosen as the final state (FS). This dissociation process on the cc 1 site requires to overcome an energy barrier of 2.44 eV with a reaction exothermicity of 2.79 eV, which is consistent with the previous study (energy barrier of 2.18 eV and reaction exothermicity of 2.70 eV) and is comparable with that of graphene (energy barrier of 2.95 eV) . There is a significantly high energy barrier of 5.23 eV, preventing chemisorbed H atom associated with H 2 molecule.…”

“…Figure displays the optimized structures of pristine PG, B‐doped PG, and N‐doped PG. The pure PG sheet fully relaxed involving its lattice constant, which is predicted to be 7.204 Å, and the predicted C═C and C─C bond distances are 1.311 and 1.534 Å as shown in Figure A, which is agreed with the previously published values (1.34 and 1.55 Å) . Subsequently, doping boron (nitrogen) atom into the PG creating the B‐doped (N‐doped) PG is also studied as depicted in Figure B,C.…”

“…The structures and physical properties of pristine pentagraphene (PG), penta-CN 2 monolayer, and penta-CB 2 monolayer have been predicted by the theoretical computations. [30][31][32] The pristine, boron-, and nitrogen-doped PGs have been studied and exhibit well catalytic activity for CO oxidation previously. [33][34][35] However, to our best knowledge, the dissociation mechanism of hydrogen molecule on pristine, B-, and N-doped PG is not illustrated.…”

“…The pure PG sheet fully relaxed involving its lattice constant, which is predicted to be 7.204 Å, and the predicted C═C and C─C bond distances are 1.311 and 1.534 Å as shown in Figure 1A, which is agreed with the previously published values (1.34 and 1.55 Å). 30,44 Subsequently, doping boron (nitrogen) atom into the PG creating the B-doped (N-doped) PG is also studied as depicted in Figure 1B,C. The relaxed lattice constant increases to 7.242 Å in the case of the B-doped PG but with similar lattice constant of 7.204 Å in the case of the N-doped PG.…”

“…Boron and nitrogen are the most often used dopants because their similar electronic structure and size to carbon permit them to substitute into the substrate with minimal strain, maintaining the overall carbon nanomaterials structure. The structures and physical properties of pristine penta‐graphene (PG), penta‐CN 2 monolayer, and penta‐CB 2 monolayer have been predicted by the theoretical computations . The pristine, boron‐, and nitrogen‐doped PGs have been studied and exhibit well catalytic activity for CO oxidation previously .…”