Abstract
Friction measurements have been made on a series of layer lattice compounds selected from a number of different crystal systems. Experiments in ultrahigh vacuum confirm the vapor lubrication mechanism for natural graphite, pyrolytic graphite, and boron nitride. For all other lamellar solids studied there was no evidence that vapor lubrication played a role in the sliding mechanism. It is likely that vapor lubrication applies to lamellar solids only when relatively high specific forces are acting between the layers.