Kinematic theory of diffraction by matter of any kind and the theory of liquids

An expression for the intensity function scattered coherently by an arbitrarily distorted lattice has been derived which degenerates under well-defined conditions to the well-known formulae valid for crystals, liquids and gases or amorphous substances. A new method for the analysis of the radial distribution function (RDF) of simple liquids has been suggested. RDF curves for liquid argon near the triple point have been analysed to obtain the distance statistics of neighbours and their coordination numbers. Using the first-neighbour statistics an expression for the partition function for matter of any kind and, in particular, for simple liquids has been deduced.