Structure Analysis of Multiphase Systems by Anomalous Small-Angle X-ray Scattering

Dragomir Tatchev (1, 2)

1 SF3
2 Institute of Physical Chemistry - BAS

The theory of the small-angle scattering is reviewed with special attention paid to the anomalous scattering and multiphase systems. A general equation describing the scattering of a multiphase system as a sum of scattering functions of each of the phases, as if it scattered alone in a two phase system, and interphase interference scattering functions is derived. These scattering functions depend only on the spatial distribution of the phase boundaries, but not on the scattering density. Contrast variation techniques are most rewarding when the scattering density of only one phase can be varied. For ASAXS, this means the most favorable is the case in which resonant atoms are contained in one phase only. The general equation involves n(p-1) unknown partial atomic number density differences, where p is the number of phases and n - the number of the different atom types in the sample. These partial atomic number density differences can be found if a suitable structure model is applied to calculate the phase scattering functions. Then, the phase compositions and densities can be calculated by solving a system of linear equations incorporating the atom number conservation law. The partial structure factors formalism is also reviewed. Corresponding equations for a system of n types of atoms and p phases are derived. The number of independent partial structure factors is p(p-1)/2 and depends on the number of phases, but not on the number of the types of the atoms in the sample, as in the case of wide angle scattering.

Mots clés: Physical Sciences

Dragomir Tatchev. Structure Analysis of Multiphase Systems by Anomalous Small-Angle X-ray Scattering. Philosophical Magazine, 2008, 88 (12), pp.1751-1772. ⟨10.1080/14786430802279760⟩. ⟨hal-00513925⟩