STUDIES ON THE BAND STRUCTURES OF SOME LOW-TEMPERATURE SUPERCONDUCTORS

摘要

In the present article, the electronic energy-band structures of 20 series of low-temperature superconductors were investigated employing the tight-binding method within the extended Huckel approximation. The energy bands, the densities of states, and the crystal orbital overlap populations of them are discussed. It is found that, for the crystals in the same series with the same structure type and the component elements in the same group of the periodic table, their overall energy-band structures are similar to each other. The analysis of their chemical bondings shows that the stronger bonding is generally correlated with the lower superconducting transition temperature to some extent. The higher T-c's of 4d metals or compounds relative to those of the corresponding 5d crystals are mainly due to the difference of the electronegativities of metal atoms, while the steric effects play a more important role in the higher T-c of 4d crystals than do those of the corresponding 3d crystals. (C) 1997 John Wiley & Sons, Inc. [References: 65]