Extended-Hückel Energy Band Structures of Transition Metal Compounds with One-Dimensional Crystal Geometries Basic Equations and Computational Results for Bis(2 ,5-dimethyl-N ,N′-dicyanoquinonediimine) copper (I)

Abstract

Using symmetry adapted basis sets of linearly combined Bloch sums, we summarize the basic equations for one-dimensional energy band structure calculations of extended-Hückel type such as SCC (Self-Consistence of Charge) and SCCC (Self-Consistence of Charge and Configuration). In addition to the considerable computational savings achievable by this technique, its main advantage is that band indexing difficulties can be systematically excluded. Furthermore, it turns out that backtransformations into the original atomic orbital basis are unnecessary throughout. As an illustrative example, we document the energy band structure of a one-dimensional model geometry of highly conducting bis(2,5-dimethyl-N,N′-dicyanoquinonediimine)copper(I) (2,5-DM-DCNQI)2Cu. In spite of its one-electron nature, the outlined energy band structure calculation method appears to be useful to rationalize the unusual electronic properties of this “organic metal”.