2H-MoS2 is a semiconductor with a hexagonal layered structure. Each Mo atom is prismatically coordinated by six S atoms. Our in situ X-ray diffraction results indicate that, upon intercalation, the MoS2 host lattice undergoes a first order phase transition in which the Mo coordination changes from trigonal prismatic to octahedral (1T structure). The driving mechanism for this structural change is discussed in terms of a charge transfer from the lithium to the host and in terms of the respective energy-band diagrams for 2H and 1T polytypes. Intercalation-induced reversals in the relative stability of trigonal–prismatic and octahedral phases may also be expected in other semiconducting hosts.

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The crystal structures of the intercalation compounds of LixTiS2 are investigated by neutron diffraction for x = 0.12, 0.33, 0.67, and 1.0. The Li atoms are shown to preferentially occupy the octahedral sites in the van der Waals gaps of the host TiS2 lattice for all values of x and no evidence for three-dimensional Li ordering is observed.

The band structure of rhombohedral graphite has been investigated using the nearest-neighbor tight-binding approximation. The resulting behavior of the π-bands near the Fermi surface is more complex than in the case of the Bernal stacking. The two π-bands still touch, but the touching points no longer lie on the edges of a hexagonal prism in k-space. Instead, they lie on cylinders whose axes are the edges of the hexagonal prism. The radii of these cylinders are proportional to γ1, the nearest "out-of-plane" exchange integral. The de Haas – Van Alphen effect in the rhombohedral structure may be expected to yield useful information about the magnitude of γ1.