On a rudimentary model of the W(001) surface instability and reconstruction

A simple qualitative theory of the reconstruction of the W (001) surface based on the assumption of an important role of Shockley surface states from the vicinity of the Fermi energy in the electron-phonon interaction is presented. While translational symmetry chooses state coupling via the pseudo-Jahn-Teller effect, the local symmetry determines the magnitude of the corresponding matrix elements. It appears that the in-plane reconstruction modes M?₅ and X?₃ are more promising whereas the buckled modes seem unfavourable since they lead to an ionic superstructure on the surface.