Amorphous structures of one or two types of atoms of various radii and masses and interacting by various central potentials are simulated by molecular dynamics on a computer. Fully relaxed atomic arrangements resulting from simulated annealing are investigated with the aim of getting an indication of possible mechanisms of self-diffusion, which is quantitatively studied in the following paper. Relaxation of random positions yields dense and homogeneous amorphous structures with neither microcrystals nor holes. Defective crystals, depending on the annealing rate and potentials, yield either defective crystals again or completely amorphous structures, which in some cases contain holes or channels.