Boron-induced tuning of electronic and superconducting behavior in sp2 carbon: pentagraphite C8 and B2C6

Abstract

Boron doping is a proven strategy to tune bonding and electronic states in sp² carbon, yet its quantitative effect on lattice dynamics and ability to induce superconductivity in three-dimensional carbon allotropes remain poorly understood. Here we combine density functional theory with lattice dynamics and electron–phonon coupling (EPC) analysis to systematically compare the prototypical pentagraphite C₈ with its boron-substituted analogue B₂C₆. Both frameworks are dynamically stable, as verified by phonon spectra free of imaginary modes, and ab initio molecular dynamics. Boron incorporation reshapes the π electronic states near the Fermi level, enhances the density of states, and softens key phonon branches that strengthen EPC. Consequently, B₂C₆ shows a substantially larger coupling constant (λ = 1.06) and a predicted superconducting transition temperature of 15.4 K, contrasting with non-superconducting pentagraphite (λ = 0.15). Simulated X-ray diffraction and Raman spectra are provided to guide experimental synthesis and phase identification. These results highlight boron doping as a versatile approach to engineer lattice dynamics, mechanical response, and superconductivity in sp² carbon frameworks, offering design principles for lightweight superconducting carbon materials.