MWP-fit: a program for multiple whole-profile fitting of diffraction peak profiles byabinitiotheoretical functions

Abstract

A computer program has been developed for the determination of microstructural parameters from diffraction pro®les of materials with cubic or hexagonal crystal lattices. The measured pro®les or their Fourier transforms are ®tted by ab initio theoretical functions for size and strain broadening. In the calculation of the theoretical functions, it is assumed that the crystallites have log-normal size distribution and that the strain is caused by dislocations. Strain and size anisotropy are taken into account by the dislocation contrast factors and the ellipticity of the crystallites. The ®tting procedure provides the median and the variance of the size distribution and the ellipticity of the crystallites, and the density and arrangement of the dislocations. The ef®ciency of the program is illustrated by examples of severely deformed copper and ball-milled lead sul®de specimens.

Powder diffraction in Bragg-Brentano geometry with straight linear detectors

“…Rietveld refinement (Rietveld, 1969) and whole powder pattern modelling (Ribárik et al, 2001;Scardi & Leoni, 2002) are nowadays the most common approaches of powder diffraction data analysis of crystalline materials. An important component of this methods is a description of diffraction profile width and shape.…”

Estimation of point defects concentrations in nickel subjected to high pressure torsion

“…Длина волны составляла λ = 1,54 нм, размер облучаемого участка -около 100500 мкм. Для разделения вкладов размера зерна и микродеформации в уширение пиков, а также для расчета плотности дислокаций использовали про-граммное обеспечение «CMWP-fit» [12] на основе модифицированного метода Уоррена-Авербаха.…”

“…При сопоставлении общего сопротивления ρ и сум-мы вышеописанных вкладов ρ 0 +Δρ вак +Δρ дисл +Δρ ГЗ (рис.4, а) видно, что присутствует довольно большая разница Δρ. Исходя из литературных данных [2][3][4], предположено, что эта разница обусловлена отжи-гом стабильных комплексов точечных дефектов (ли-нейным размером менее 5 нм), которые не опреде-ляются методом РСА [12]. Из соотношения C v = Δρ/ ρ vac рассчитана концентрация вакансионных ком-плексов, которая представлена на рис.…”

Thermal stability of the microstructure of severely deformed copper

“…The measured data were evaluated by the MWP fitting method. The procedure is described in detail in references [8,9]. The measured intensity profiles are fitted by theoretical line profiles and from the procedure the following parameters of the microstructure are obtained: (i) the median m and the variance σ of the log-normal size distribution function, (ii) the density ρ and the arrangement parameter M of dislocations, (iii) the q parameter, which characterizes the contrast factors of dislocations and describes the type of dislocations (edge or screw).…”