Long-range electronic correlation studies for organic and inorganic electronic systems

Whatever for the organic electronic systems or the inorganic electronic systems, the electronic correlation problem is much important one because the electronic correlation problem refers to correct estimation of energy band gap which is important for designing semiconducting electronic devices. For pi electronic systems a general formula of the long-range correlation energy Ec has been given, which includes diagonal and off-diagonal interactions. For inorganic materials(e.g.ZnO, etc) the exact calculation of the correlation effect is still lack until now. In this study we will discuss analytical calculation of the correlation effects for this important problem.