All chemical processes, from those we observe (classically) in our daily lives to the most sophisticated ones observed in the laboratory, are governed by Nature’s laws acting on the underlying microscopic constituents. Whereas the fundamental concepts of quantum mechanics have been formulated more than a century ago, the description of matter from first principles remains a serious challenge for quantum chemists. This is due to the large degree of quantum correlations in the systems, particularly manifest in so-called strongly correlated systems. Traditional methods based on the orbital model are computationally friendly, but fail to describe these strong correlations, sometimes even in a qualitative way. So, there is a strong call for accurate methods beyond the orbital method, at low computational cost. The research objective of this FWO project is to
answer to this call, using the geminal approach, which is based on the idea that strongly correlated electrons restructure pairwise together. We intend to extend and develop a newly identified class of non-orthogonal geminals, which we will submit to a large variety of chemical tests. These tests will allow for a chemical intuitive picture of these intrinsically quantum mechanical systems, connecting with the concept of atoms in molecules and the Lewis picture of chemical bonding.