Static relaxations of puckering distortions in intercalated layered solids

Abstract

Layered solids have been qualitatively characterized according to their transverse layer rigidity with respect to point-like puckering distortions. In this scheme graphite is a ‘floppy’ layer system, layered aluminosilicates contain ‘rigid’ layers and layer dichalcogenides fall between these extremes. The primary signature of layer rigidity is the dependence of the basal spacing, d( x), on composition, x, in a ternary systems A 1− x B x L where L represents the host layers while A and B are distinct guest species with radii r A < r B. Previous attempts to quantify the layer rigidity (i.e. account for d( x)) using models which employed infinitely rigid layers have been singularly unsuccessful. In the present paper a one-parameter finite layer rigidity model, which yields an extremely good fit to the composition dependent basal spacing of a wide variety of layered solids which includes the floppy and rigid extremes, is described. In this model, a healing length is introduced to quantify the static spatial relaxation of a point-like puckering distortion. Both a discrete and continuous version of the model are presented and shown to yield equivalent results. It is found that, as expected, the more rigid the host layer, the larger the healing length, the values of which are deduced for several important layered solids.