Abstract : Two-electron integrals play a key role in determining electronic properties of atoms and molecules. They also govern their interactions. Copper oxides play various roles both in nature and industry. In this work, our attention is devoted to applications of quantum theory to reactivity. In particular the role of interactions in heterogeneous catalysis. the examples chosen are in mild oxidation of alkanes and alkenes on the oxidised copper (001) surface. The methods azre tested and found to be reliable for surface energy and di usion barrier calculations. This manuscript describes a method of evaluating Coulomb integrals based on solving Poisson's equation for the associated potential. The resulting interactions are put to use in the context of periodic systems, in particular to study the surfaces of catalysts based on copper. These partially oxidised surfaces are used to selectively oxidise alkanes and alkenes in mild conditions. The DFT plane wave code ABINIT has been used to study some selective oxidation reactions on parially oxidised copper (001) surfaces.