Two-dimensional octagon-structure monolayer of nitrogen group elements and the related nano-structures

Abstract

In the purpose of expanding the family of two-dimensional materials, we predict the existence of two-dimensional octa-structure of nitrogen group elements that are composed of squares and octagons in first-principle method based on density functional theory (DFT). From our calculations, electronic structures of all monolayers show that they are semiconductors with indirect (N, P, Bi) and direct (As, Sb) band gaps (0.57-2.61eV). Nano-ribbons of three different unpassivated edges and their band structures are also investigated. Because of the reconstruction on the edges and dangling bonds, there exist ferromagnetic edge states in P, As, Sb nano-ribbons with different edges, and a Dirac point near π is found in the band structure of one specific N nano-ribbon. These structures may be useful in future applications, such as semiconductor devices, spintronics, hydrogen storage and quantum computation.

Stable, one-dimensional suspended and supported monatomic chains of pnictogens: a metal–insulator framework

“…Also the cohesive energies of 2D monolayers of group-VA elements in buckled honeycomb, symmetric or asymmetric washboard and square-octagon structures are given for comparison. [64][65][66][67][68][69] As expected, the cohesive energies of stable monatomic chains are slightly smaller than those of the corresponding monolayers, but they are rather high due to triple bonds between atoms as discussed in the next section. Also, the bond length of a 1D monatomic chain is shorter than that of the corresponding 2D monolayer.…”

“…Fig. 3 presents the variation of the total energy of the P-ZZ chain Table 1 Structural parameters and relevant energies calculated for the stable, monatomic group-VA chains: lattice constant (a); bond length in the 1D chain structure (d chain ); bond length in the 2D monolayer; bond angle (y); the cohesive energy in the chain structure (E c ); the cohesive energy of the corresponding 2D monolayer in buckled honeycomb (hb), symmetric (sw) or asymmetric (aw) washboard and square-octagon (so) structures (E c;2D ); the band gap (E g ) (with (d) indicating a direct band gap and M: metal, SM: semimetal); the band gaps corrected by HSE; and the elastic stiffness coefficient (k) 45,46,64,69 with the axial strain. Here a i is the strained lattice constant.…”

Single-orbital realization of high-temperature s± superconductivity in the square-octagon lattice

“…First-principles calculations indicate that such a planar structure is kinetically stable at low temperature [12,13] and that its energy is a local minimum [12], which suggests that the material can potentially be synthesized in laboratories. Actually, this lattice structure has attracted a lot of research interest recently because it not only is hosted by quite a few real materials [14][15][16][17] but also has various intriguing phases on this lattice that have been revealed by theoretical calculations [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35]. Here we notice another remarkable property of this 2D lattice: its band structure can have perfect Fermisurface (FS) nesting in a wide parameter regime at half filling, which easily leads to antiferromagnetic SDW order.…”

Topological node line semimetal state in two-dimensional tetragonal allotrope of Ge and Sn

“…Interestingly, tetragonal allotrope of single layer MX 2 (M=Mo, W; T=S, Se, Te) were proposed to be QSH insulator [18][19][20]. Moreover, it was theoretically proposed that except for single layer puckered and buckled honeycomb lattice structures [22], group V elements, including P, As, Sb and Bi, can form a stable 2D tetragonal allotrope composed of buckled square and octagon rings [23][24][25][26]. Remarkably, 2D tetragonal allotrope of Bi was predicted to be QSH insulator with a sizable band gap about 0.41 eV [25,26].…”