Linear, planar, and tubular molecular structures constructed by double planar tetracoordinate carbon D2hC2(BeH)4 species via hydrogen-bridged -BeH2Be- bonds

The Evolution of Electronic and Magnetic Properties of the Chain and Sheet Assemblies Based on Planar Tetracoordinate Carbon C2Al4(CH3)8

The new planar tetracoordinate carbon (ptC) compounds have received significant research attention in recent years. The present study is devoted to investigating the structural, electronic, and magnetic features of one-dimensional chains and two-dimensional sheets composed of C₂Al₄(CH₃)₈ building blocks. All possible condensations were studied, and the stabilities of different ptC assemblies were compared. Several properties such as energy gap, dipole polarizability, electronic excitation energies, and nucleus chemical shift were computed for chains up to 7 and sheets up to 16 units. A systematic analysis was performed to assess the impact of condensation pattern and number of units on the calculated properties. Topological analysis of density and electron localization functions reveals that Al-C bonds in the considered ptCs have mixed covalent/ionic character with larger ionic contribution. It is found that the electronic spectra of the condensed ptCs exhibit red shift toward larger wavelengths when compared to the C₂Al₄(CH₃)₈ building block. The amount of red shift enhances with increasing number of units. We show that the stability trend, predicted by electronic and magnetic descriptors, are in qualitative agreement with the thermodynamic stability obtained through Gibbs free energy change of condensation reaction.

Viable aromatic BenHn stars enclosing a planar hypercoordinate boron or late transition metal

Similar to B_n rings, star-like Be_nH_n rings can serve as the n-electron σ-donors for designing species with planar hypercoordinate atom.

Stabilization of beryllium-containing planar pentacoordinate carbon species through attaching hydrogen atoms

The destabilization issues, like high charges, small HOMO–LUMO gaps, and dispersed MOs, etc. can be eliminated via attaching hydrogen atoms.

Beryllium–beryllium double-π bonds in the octahedral cluster of Be2(μ2-X)4 (X = Li, Cu, BeF)

Double π_Be–Be bonds formed by the help of s¹-type electron donating ligand.

Prediction of a new BeC monolayer with perfectly planar tetracoordinate carbons

Recently, there has been a growing interest in exploring planar hypercoordinate carbons in two-dimensional nanostructures. However, atomic monolayers with ideal planar hypercoordinate carbon are quite rare due to the challenge in stabilizing the exotic motifs. We predicted a global minimum two-dimensional BeC monolayer using the global particle-swarm optimization method. Each carbon binds peripheral four atoms in the same plane, forming a perfectly planar tetracoordinate carbon moiety. The cohesive energy, phonon-spectrum and mechanical stability criteria confirm the stability of monolayer BeC. In addition, the BeC monolayer has a large in-plane stiffness (145.54 N m^-1) and thermo-dynamical stability (up to 2000 K). Furthermore, BeC is an indirect semiconductor with a band gap of 1.01 eV and possesses exceptionally high carrier mobilities (∼10⁴ cm² V^-1 s^-1), rendering it suitable for application in electronics and photoelectronics.