Nonlinear theory of domain walls and domain effective interactions in intercalation compounds

Abstract

A nonlinear theory of Daumas-H\'erold dislocations in intercalation compounds is presented. Purely elastic effects in a nonequilibrium partly intercalated situation, and also the case of equilibrium with a guest reservoir are considered. In the first case, the local deformations of the host show spatially damped oscillations which give rise to strong interference effects in the domain-wall energetics. They provide a stabilizing mechanism against island conglomeration during intercalation and help to explain the persistence of domains in these compounds. Realistic domain-wall energies and energy barriers to relative motion of intercalate domains are calculated for the entire range of guest species intercalating into graphite. The calculations presented include different host-layer stacking arrangements and wall configurations for stage-2 compounds. The dependence of the energetics on intercalate guest and wall configurations is complex and unexpected, profoundly affecting the kinetics of intercalation. This suggests an explanation to the unusual behavior of sodium and other guest species with slow kinetics and imperfect intercalation. In the second case, samples in equilibrium with the guest reservoir are considered by the inclusion in the energetics of the chemical potential. The main effect is to reduce the domain-wall widths and remove energy barriers. Other experimental implications of this model are also discussed.