07/03/2026
Why do some snowflakes form needles while others become flat platelets?
Join us for the first Maxwell Lecture of 2026 as Dr Carla Molteni explores how temperature shapes ice crystals at the molecular level.
Date: Thursday 12 March
Time: 6–7pm
Room: KIN G13
Abstract:
Ice crystals are among the most familiar and fascinating structures in nature. From intricate snow crystal patterns to compact prisms, their shapes reflect the physics of how water molecules arrange and grow in solid form. While we often associate ice with complex, branching structures at high humidity, even simple, compact crystals formed at low humidity display a remarkable variability that is not yet fully understood.
At low humidity, ice forms hexagonal prisms whose shape strongly depends on temperature. At some temperatures, crystals grow into long, slender needles; at others, they develop into thin, flat platelets. What determines this change in geometry?
Using computer simulations, we investigate how ice grows at the molecular level. By estimating the growth rates of different crystal surfaces, we uncover the microscopic mechanisms that control the overall crystal shape and explain its temperature dependence.
Understanding how ice crystals form and evolve is important in atmospheric science, climate modelling, aviation, winter sports and cryopreservation. Despite being a substance we encounter every day, ice continues to challenge scientists with open questions. By combining physics and computational modelling, we can reveal the rich variety of shapes observed in nature emerge from molecular interactions.
