On the Lindemann criterion in 2D

Molecular-dynamics simulations suggest that in 2D screened Coulomb solids melt when the r.m.s. displacement of particles in local co-ordinate systems exceeds ~ 10% of the lattice period, close to the Lindemann criterion in 3D. This criterion is over-estimated in the co-operative motion model, but under-estimated in the Einstein model, because during melting a 2D solid is a mixture of both ordered and disordered phases.