Beschreibung:
A general cluster integral formalism is developed for the calculation of the molecular pair distribution function. A hybrid between a Mayer graph and a Feynman diagram is associated with the cluster integrals. The formalism is used to derive the London-Placzek formula for the pair distribution function of perfect Bose-Einstein and Fermi-Dirac gases and the Debye-Huckel distribution function for a low density electron gas.