Varieties of charge transfer and bonding between layers in misfit layer compounds (MX)(x)TX2

The features in interlayer bonding, structure and physical properties of the misfit layer compounds like (MX)(x)TX2 (with M=Sn, Pb, Bi, Sb, Rare-earth elements; X=S, Se and T = Ti, Nb, Ta, V, Cr) are discussed compared with the thermodynamic properties and electronic structures of two types of isomeric equilibrium molecular charge-transfer complexes (of CTC-I and CTC-LI types). Analogous to the CTC-I and CTC-II cases a possibility of two types of a 'reverse' charge transfer from X atoms of the TX2 layer toward the MX layer, besides the known charge transfer from the MX to the TX2 layer, is proposed to describe the bonding between layers in the misfit compounds. The X atoms of the TX2 layer that are involved In the interaction with the MX layer similar to that in CTC-I or CTC-II can act as effective scatterers or localization centers of the conduction electrons in the TX2 layer. The localization of the transferred electrons in the MX layer depend on a type of the charge transfer (CTC-I or CTC-II). The stabilization of the CTC-II structure as the temperature is lowered results in carrier localization in both the MX and TX2 layers. (C) 1997 Elsevier Science S.A.