MATERIALS SCIENCE AND CHEMISTRY

Phase transitions are striking, abrupt transitions in the structure of a substance. Some of them are familiar from everyday experience, for example the freezing of water, or the condensation of vapor to form mist or clouds in the atmosphere. But how the first stable clusters of the new phase actually form, and what they look like, still remains largely unknown. In the case of condensation, the smallest stable droplets contain between about ten and a few hundred atoms, depending on temperature and pressure. This is why the classical, continuous theory is a rather inaccurate description of phase transitions, and a complete theory of this fundamental process remains lacking. Physicist Jürg Diemand from University of Zurich and his team investigate the formation of such nano-droplets out of the vapor phase with extremely large molecular dynamics simulations (up to 8 billion atoms, 56 million time-steps, on up to 32,000 CPUs).