We discuss the electronic structure, lattice dynamics, and electron-phonon interaction of the newly discovered superconductor LaO${}_{0.5}$F${}_{0.5}$BiS${}_2$ using density-functional-based calculations. A strong Fermi surface nesting at $\mathbf{k}=(\pi ,\pi ,0)$ suggests a proximity to charge-density-wave instability and leads to imaginary harmonic phonons at this $\mathbf{k}$ point associated with in-plane displacements of S atoms. Total energy analysis resolves only a shallow double-well potential well preventing the appearance of static long-range order. Both harmonic and anharmonic contributions to electron-phonon coupling are evaluated and give a total coupling constant $\lambda \simeq 0.85$, prompting this material to be a conventional superconductor contrary to structurally similar FeAs materials.

• Received 8 August 2012

DOI:https://doi.org/10.1103/PhysRevB.87.115124