X-ray diffraction in disordered paraelectric crystal structures with polar clusters and the g parameter

In the crystal structure analysis of disordered structures consisting of randomly distributed polar lattice cells, additional information on the range of order can be obtained by introducing the g parameter in the structure-factor equation F(h) = A(h) + igB(h). In the case of perfect disorder, the parameter g tends to zero; however, in the case of local order, the crystal structure contains small polar clusters and the g parameter becomes greater than zero (0 < g < 1). The physical meaning of the g parameter is explained in terms of the peculiar features of X-ray diffraction in disordered structures.