The transport of Na+ and Li+ in twinned quartz, under the influence of an electric field, was simulated by using molecular dynamics techniques. A comparison of bulk transport, with transport along twin boundaries, showed that the cations were trapped within twin walls for weak fields directed along the crystallographic c-axis. Stronger fields led to transport along twin walls, with a significantly lower mobility than that in the bulk. When the field was directed along [110], the transport in the wall was faster than that in the bulk. Preferential cation trapping in the twin walls was observed when the field was directed out of the plane of the wall.

Anisotropic Ionic Transport in Quartz - the Effect of Twin Boundaries. M.Calleja, M.T.Dove, E.K.H.Salje: Journal of Physics - Condensed Matter, 2001, 13[42], 9445-54