Structural relaxation of the chlorite surface imaged by the atomic force microscope

The surface structure of the layer silicate mineral chlorite has been imaged at nearatomic resolution using an atomic force microscope (AFM). The chlorite structure consists of a 2:l talc-like layer and a brucite-like interlayer sheet. The AFM clearly resolves the OH groups of the brucite-like interlayer sheet and the bases of the SiOo tetrahedra of the talc-like sheet. The imaged surface structures of both the talc- and brucitelike layers are generally consistent with that of the bulk structure. The mean unit-cell distances (a: 5.31 + 0.31, b:9.74 + 0.80 A) are within I and 5ol0, respectively, of those calculated for the known structure. However, some structural relaxation of the talc-like surface is observed. This relaxation manifests itself as a systematic shortening and elongation of both a and b across the layer and probably results from a concertina-like readjustment of the surface after cleaving. The bruciteJike layer does not exhibit similar behavior.