Atoms are packed in amorphous materials

Many substances around us, from table salt and sugar to most metals, are arranged into crystals. Because their molecules are laid out in an orderly, repetitive pattern, much is understood about their structure. However, a far greater number of substances — including rubber, glass and most liquids — lack that fundamental order throughout, making it difficult to determine their molecular structure. To date, understanding of these amorphous substances has been based almost entirely on theoretical models and indirect experiments. A UCLA-led research team is changing that. Using a method they developed to map atomic structure in three dimensions, the scientists have directly observed how atoms are packed in samples of amorphous materials. The findings, published today , may force a rewrite of the conventional model and inform the design of future materials and devices using these substances.