Band Gap Engineering and 14 Electron Superatoms in 2D Superoctahedral Boranes B₄X₂ (B, N, P, As, Sb)

Abstract

Band gap tuning in 2D monolayers is one of the most attractive approaches in design and production of new atomically thin semiconductors. Following our recent computational design of stable two-dimensional octahedral boranes, we present comprehensive computational study of electronic structure, stability and properties of members belonging to family B4X2 (X = B, N, P, As, Sb). We select 15 group atoms (pnictogens) as apical substituents to stabilize quasi-octahedral units by delocalized bonding and create interlayer “pressure” caused by vertically aligned lone pairs. We first substitute apical B atoms by N and then go down the 15 group to capture electronic structure trends. B→N substitution opens band gap, while further substitution consistently narrows band gap. We revealed elegant band gap trend which is inversely proportional to the size of octahedral units. Thus, old as world isoelectronic substitution could be used for band gap engineering in superoctahedral 2D boranes and other monolayers. We also discovered superatomic bonding in B4As2 and B4P2 octahedra which agrees with their exceptional stability (up to 800 K) and magnetic response properties. Remarkably, both B4As2 and B4P2 units have 14 valence electrons, making them exceptional examples of stable nonconventional electron count of spherical aromaticity. Alongside with a considerable negative formation energy and phonon stability, B4As2 has extremely low exfoliation energy of 0.02 eV/atom implying probability of synthetic route from a putative bulk material. It gives a strong basis to believe in possibility of experimental fabrication of B4As2 monolayer which can serve as alternative to MoS2 and silicon.

Two-dimensional AlB4/Al2B2: high-performance Dirac anode materials for sodium-ion batteries

“…The maximum phonon frequencies of AlB 4 (851.19 cm À1 ) and Al 2 B 2 (1088.29 cm À1 ) are higher than those of BeB 2 (808 cm À1 ), Y 2 B 2 (636 cm À1 ), BAs (834 cm À1 ), and octahedron B 4 N 2 (600 cm À1 ). 9,[33][34][35] The thermal stabilities of AlB 4 and Al 2 B 2 are assessed through AIMD simulations at 400 K (Fig. S2, ESI †).…”

FeP2 monolayer: isoelectronic analogue of MoS2 with excellent electronic and optical properties

“…Chemical bonding analysis of the FeP 2 monolayer was performed using the solid-state adaptive natural density partitioning (SSAdNDP) method, 58 which was developed by Boldyrev et al 59–62 We chose the def2-TZVP 63 basis set as the plane-wave projection of the electron density matrix. The climbing-image nudged elastic band (CI-NEB) method 64 was employed to study the adsorption kinetics of O 2 molecules.…”

On the Precise and Continuous Regulation of the Superatomic and Spectroscopic Behaviors of the Quasi-Cubic W4C4 Cluster by the Oriented External Electric Field

“…In the past 30 years, a series of superatoms, including superhalogens, ,− superalkalis, − magnetic superatoms, − and so forth, have been successively identified, and their potential in designing novel cluster-assembly materials with tailorable properties have also been explored. , For instance, Guo and co-workers provided evidence that, regardless of the adsorption type, the VLi 8 superatom adsorbed on the graphene maintains its structural stability and exhibits strong ferromagnetic coupling . Additionally, a recent photoelectron spectroscopic experiment verified that the diatomic WC cluster could be considered as a superatomic analogue of Pt because it has the similar electronic structure with Pt .…”