Cooperative mercury motion in the ionic conductor Cu2HgI4
  We present the observation of glass-like dynamic correlations of mobile mercury ions in the ionic conductor Cu2HgI4, detected in both NMR and nonlinear conductivity experiments. The results show that dynamic cooperativity appears in systems seemingly unrelated to glassy and soft arrested materials. A simple kinetic two-component model is proposed, which seems to provide a good description of the cooperative ionic dynamics. 
Damjan Pelc, Igor Markovic and Miroslav Pozek
cond-mat.mtrl-sci cond-mat.stat-mech