Effect of substitutional impurities on the electronic states and conductivity of crystals with a half-filled band

Low-temperature quantum corrections to the conductivity and density of stat es (DOS) of crystals with substitutional impurities are calculated. Summing the leading logarithmic corrections to the DOS, its energy dependence near half-filling is obtained for a two-dimensional (2D) square crystal and a 3 D simple cubic crystal. It is shown in two dimensions that substitutional i mpurities do not suppress the van Hove singularity in the middle of the ban d, though they change its energy dependence strongly. Weak disorder due to substitutional impurities in the 3D lattice results in a shallow dip in the center of the band. The calculation of quantum corrections to the conducti vity of a 2D lattice shows that a well-known logarithmic localization corre ction exists for all band fillings. Furthermore, the magnitude of the corre ction increases as half-filling is approached. The evaluation of the obtain ed analytical results shows evidence of delocalized states in the center of the band of a 2D lattice with substitutional impurities.