Abstract

Many competing models for decagonal AlCoNi exist based upon experimental X-ray diffraction or electron microscope studies. We supplement this experimental data with considerations of total energy to deduce a structural model that specifies uniquely the positions and chemical identity of all transition metal atoms and most aluminum atoms. All atoms occupy sites of low energy and force. Our model is in excellent agreement with experimental electron microscopy data. We understand the energetics favoring our proposed ideal structure and low lying excitations that include both chemical and phason disorder.