A 30 ps portion of the Cs-beidellite, 1/3 water monolayer MD simulation animation (350–380 ps). Interlayer species are represented as described in Plate 1. The three highlighted water molecules (lighter blue) reside within six-oxygen cavities of the lower clay surface for extended time periods. One of these water molecules, located near the top of the small view at the top left of the animation, and nearly hidden by a 2 Cs+-2 water molecule complex, stays within the six-oxygen cavity for the 30 ps length of this animation. See Additional file 3 to access the animation.