The implantation of Ni ions into pure Al leads to the formation of similar to 10 nm amorphous zones (AZ) which induce diffuse rings in the diffraction pattern in addition to the diffraction spots of the crystal. Measurements by energy dispersive spectrometry and electron energy loss spectrometry attributed to the amorphous zones an average Ni concentration of 25 at%. The exact structure of these AZ is still unknown. The structure is characterized here by both the total and partial radial distribution functions (RDF). Structure factor deduced from experiments is compared to calculated one. For this purpose, molecular dynamic (MD) simulations are used to model the AZ structure. The RDF are determined using this structure and analytical calculation of the diffraction pattern is achieved. Simulations of the diffraction pattern of the simulated MD sample using both a kinematic and a dynamic approach are achieved to refine the analytical procedure used on the experimental diffraction patterns. It appears that the amorphous structure is well reproduced by the MD simulations. Analytical calculation reveals the presence of a well-established chemical order in the amorphous material. (C) 2000 Elsevier Science B.V. All rights reserved.