Series expansion calculation of the elastic neutron diffuse scattering: Ice Ih

Abstract

A theoretical systematic method for the evaluation of the neutron elastic, coherent, diffuse scattering intensity of ice Ih is presented. For each Q vector, the latter is expressed directly as a series expansion of graphs. This technique is analogous to the Ising susceptibility calculation and avoids the explicit use of individual correlation functions. Therefore the series can be easily and exactly expanded to rather high orders. For the computation of the scattering intensity, the correlation model used is based on the ice rules and the normalized probability is written according to Nagle's formulation. The resulting series is convergent and theoretical isodiffusion patterns have been drawn by extending the series up to the 8th order; the accordance with experiment is good.