Theory of X-ray measurement of microfibril angle in wood .2. The diffraction diagram - X-ray diffraction by materials with fibre type symmetry

A diffraction intensity function for material bodies composed of arrays of crystalline fibres such as occurs with the cellulose of wood has been derived. It is implied in the analysis that the crystalline fibres making up the body have fibre symmetry-that there is a tendency for groups of fibres to have one set of crystal axes parallel while in the orthogonal direction the axes assume a low degree of order. It is further assumed that the patterns of the angular arrangement of the fibre groups relative to one axis of the body is independent of the direction about that axis. These conditions are believed to be compatible with the cellulosic structure found in wood. Thus it becomes possible to calculate the expected diffraction intensity profiles of realistic (and therefore complex) models of wood. This has aided the interpretation of the reflections from the (040) crystal planes of cellulose which are contaminated by low level reflections from other crystal planes, and it has been found that it might be possible by conjoint analysis of the paratropic (002) reflections and the diatropic (040) reflections to measure the complete cell wall planar microfibril angle distribution and the shape of the cell wall cross-section.