A two-dimensional TiB₄ monolayer exhibits planar octacoordinate Ti

Area of Science:

• Materials Science
• Chemistry
• Condensed Matter Physics

Background:

• The advancement of two-dimensional (2D) nanomaterials has spurred interest in identifying materials with planar hypercoordinate atoms.
• Planar hypercoordination is a key concept in modern chemistry, particularly relevant to novel material discovery.

Purpose of the Study:

• To predict and characterize a novel two-dimensional (2D) material exhibiting planar hypercoordination.
• To explore the stability and potential synthesis of this new material.
• To investigate the underlying mechanisms stabilizing the planar hypercoordinate structure.

Main Methods:

• Employed swarm-intelligence structure search combined with first-principles calculations.
• Conducted systematic ab initio calculations to assess thermodynamic and dynamic stabilities.
• Analyzed geometric fit and electron transfer mechanisms.

Main Results:

• Predicted a novel 2D TiB4 monolayer featuring a planar octacoordinate titanium (Ti) atom.
• The Ti atom is bonded to eight boron (B) atoms in a perfect plane, achieving the highest Ti coordination in 2D materials.
• Demonstrated superior thermodynamic and dynamic stabilities, suggesting high feasibility for experimental synthesis.

Conclusions:

• The stabilization of the 2D TiB4 monolayer is attributed to the geometric compatibility between Ti and the B ring, and electron transfer.
• Designed and discussed other 2D transition metal borides (TMB4) with quasi-planar octacoordinate atoms.
• This work provides a framework for discovering new 2D hypercoordinate materials.