Thermal expansion of the LiF(0 0 1) surface

The lattice constant at the surface of a LiF(0 0 1) crystal is measured by He atom diffraction at temperatures of 110–720 K. Contrary to previous reports, the surface thermal expansion coefficient is found to be the same within the precision of the experiments as for the bulk. The LiF(0 0 1) surface remains in the ideal (1 × 1) structure without any significant lateral contraction or expansion in the surface plane, making it one of the few examples of an ideally terminated surface.