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 Gamma-R direction.