Fermi-surface-induced lattice distortion in NbTe₂

The origin of the monoclinic distortion and domain formation in the quasi-two-dimensional layer compound NbTe₂ is investigated. Angle-resolved photoemission shows that the Fermi surface is pseudogapped over large portions of the Brillouin zone. <i>Ab initio</i> calculation of the electron and phonon band structure as well as the static RPA susceptibility lead us to conclude that Fermi surface nesting and electron-phonon coupling play a key role in the lowering of the crystal symmetry and in the formation of the charge density wave phase.