Electron momentum density of TTF-TCNQ (tetrathiafulvalene-tetracyanoquinodimethane) studied by Compton scattering

We have investigated the electronic structure of the quasi-one-dimensional organic metal TTF-TCNQ by measuring Compton scattering from single crystals . The measured profiles are significantly anisotropic. The directional anis otropies were compared with those derived by two different theoretical appr oaches. The first is the molecular orbital approximation: Compton profiles were calculated for the TTF and TCNQ molecules, separately, and then these were superposed. In spite of the simplicity of this approach, the agreement is reasonably good, implying that the electronic wave functions of TTF and TCNQ in the crystal are not very different from those of isolated molecule s. The second approach is an nb initio pseudopotential band-structure calcu lation. The agreement is better, presumably due to the more accurate descri ption of the crystallinity (including, for example, the inter-molecule char ge transfer and band formation).