Axial diffraction of curved lattices: geometrical and numerical modeling. Application to chrysotile
Devouard, Bertrand; Baronnet, Alain
European Journal of Mineralogy Volume 7 Number 4 (1995), p. 835 - 846
published: Aug 1, 1995
manuscript accepted: Feb 6, 1995
manuscript received: Oct 17, 1994
ArtNo. ESP147050704011, Price: 29.00 €
Abstract A geometrical model is proposed for the non-periodic networks of curved or wrapped lattices which can be considered as built up by the stacking of cylindrically deformed layers separated by easy glide planes. This model describes the modifications of stacking induced between adjacent layers by the curvature, as well as the topology of the related diffraction patterns. Application of numerical two-dimensional Fourier transforms to model structures of chrysotile lead to the simulation of  zone axis diffraction patterns of this mineral. These numerical simulations point out the effect of the stacking sequence of the cylindrical layers in terms of shift components along the curved b direction (radial order, polytypism or disorder). They are compared to numerical Fourier transforms of high-resolution electron micrographs, since diffraction patterns of chrysotile single fibers have not been recorded so far along this zone axis. Incidentally, the five-fold symmetry of this zone axis is experimentally evidenced.