Electronic structure of tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) and Nb by the pseudofunction energy-band technique

The pseudofunction energy-band method is a full potential, ab initio technique with no adjustable parameters. The basis function is related to the pseudofunction used to create ab initio pseudopotentials. Orthogonalization of the pseudofunction to the core states is accomplished as in the augmented plane-wave method (APW) or linear augmented plane-wave method. The applicability of the pseudofunction method to both localized bonding as in molecules or to delocalized bonding as in metals is demonstrated with application to Nb and tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ). The electronic and structural properties calculated for Nb agree well with that of the APW and Korringa-Kohn-Rostoker (KKR) methods. The energy bands obtained from an ab initio self-consistent energy-band calculation for TTF-TCNQ are successful in providing new insight into the properties of TTF-TCNQ. The computed optical properties, Fermi surface wave vector, and charge transfer agree quantitatively with experiment for TTF-TCNQ.