Surface structure solution by X-ray diffraction: structure completion with positivity and atomicity constraints

Abstract

We propose a method for the solution of surface structures from X-ray diffraction based on the phasing of measured structure factor amplitudes in two stages. First, incorporation of calculated amplitudes and phases of the structure factors of the known underlying bulk structure, together with an iterative algorithm that ensures the positivity of the electron density enables the determination of the amplitudes and phases of the surface structure factors contributing to the crystal truncation rods. Second, inclusion of these structure factors in an iterative algorithm based on Sayre's equations enables the phasing of the superstructure rods.