On the use of the whole eigenvalue spectrum to obtain single molecule band structures and solid band gaps for molecular electronics studies

Abstract

A Density Functional microscopic model of C-60, consisting of seven molecular orbitals (3 occupied and 4 empty), was employed to get the best values for the half-width and the scanning distance of the mathematical function used to obtain the theoretical DOS spectrum. It is found that the convolution of the whole eigenvalue spectrum with a Gaussian function should be made with values of 0.1 eV for both, the broadening parameter and the scanning distance. The theoretical calculation of the VB-CB band gap for the solid from results belonging to isolated C-60. is in a relatively good agreement with most experimental results. We were able to simulate the "experimental" band gap starting from the theoretical DOS spectrum and using some experimental data. Regarding the HOMO-LUMO gap, the isolated molecule results are in very good agreement with experimental results for solid C-60. Finally it is suggested that experimentalists select their results based on in a priori knowledge of theoretical results because they intend to calculate some properties needing them.