Lattice dynamics and anomalous bonding in rhombohedral As: First-principles supercell method

The pending understanding of lattice dynamics in rhombohedral $(A7)$ arsenic has been resolved by the first-principles supercell method. An anomalous bonding with considerable stretching force constant is found between atoms spanning the alternately first and second nearest neighbors, which stabilizes the layered $A7$ structure by suppressing the appearance of imaginary phonon modes. This anomalous bonding, as a result of Peierls distortion, is traceable from the undistorted simple cubic lattice exhibiting giant Kohn anomaly at the R point due to Fermi-surface nesting along the Γ-R direction.