Coupled atom and electron motions on the si(001) surface from first-principles molecular dynamics and their visualization by a video

The abrupt change in the physical environment embedding the atoms on the surface layers produces a variety of effects that are not easy to explain. First-principles molecular dynamics calculation is a tool for clarification of such problems. On the Si(001) surface the alternating tilt of dimers in the ground state and their thermally activated anharmonic flipping are confirmed by tune-dependent Car-Parrinello-like calculations. The simultaneous evolution of the occupied surface states explains why dimers appear symmetric in room-temperature scanning tunneling microscopy images, whereas spectroscopic and low temperature measurements indicate tilted dimers. The most important motions of the dimer atom rows are visualized by a video 1.