A team of scientists have solved a previously unsolved scientific mystery, finding the minimum number of water molecules that must come together in order for them to be able to form a real ice crystal.
Ice crystals also have small beginnings – even smaller than previously believed. Already 475 water molecules can form a real crystalline structure; initial attempts can be discerned with 275 molecules upwards, as a cooperation of scientists from Göttingen and Prague has discovered. It was previously thought that around 1000 molecules were the minimum necessary for a complete crystal. The new lower limit for ice crystals was determined by researchers working with Thomas Zeuch from the University of Göttingen in an experiment developed by Udo Buck from the Göttingen-based Max Planck Institute for Dynamics and Self-Organization.
Nothing is as natural for us as the behavior of water. This includes what we might have experienced in summer – a long forgotten water bottle in the freezer compartment shatters. "However, this is actually very unusual." Udo Buck still becomes enthusiastic about this after a long career as a scientist: "Strangely enough, water is one of the few substances known to us which occupies a larger volume in the solid state than in the liquid one." The Research Group Leader at the Max Planck Institute for Dynamics and Self-Organization in Göttingen has achieved a ground-breaking result with the smallest water ice crystal. His co-authors, including Thomas Zeuch's group at the Institute for Physical Chemistry at the University of Göttingen, and a researcher from the Technical University in Prague, have further improved an experiment that Buck has been developing since the early 2000s.
The cooperation in Göttingen does not, however, investigate the formation of ice from liquid water. Their discovery provides insights into processes whereby water vapor condenses directly to tiny ice crystals at low temperatures. "These processes play an important role in the upper layers of the atmosphere," emphasizes Buck, "and also in our planetary system." The new finding could also assist climate research to improve its models of the atmosphere. So what did the researchers find out exactly?
In ice crystals, the water molecules arrange themselves in a six-sided, or hexagonal, to use the scientific term, spatial lattice. Each water molecule forms chemical bonds, so-called hydrogen bonds, to four adjacent molecules. This honeycomb crystal lattice of water ice requires more space than liquid water, which is unusual. As long as the water clusters have not reached the minimum size for a crystal, the Göttingen experiment presents them with a dilemma. The experiments take place at around minus 180 to minus 150 degrees Celsius – the molecules are therefore much too cold for a liquid. For a crystal, however, they are still too few in number. The tiny clusters escape this quandary by forming a type of liquid that has clotted in the cold: they form a rather disordered, "amorphous" spatial lattice.
This so-called infrared spectroscopy of such small clusters works only with a few tricks, however. The experiment initially produces individual, cold clusters. The clusters then fly at more than the speed of sound through a chamber in which each collects one individual sodium atom. They then fly on for around 240 microseconds (millionths of a second) to the actual measurement. The attached sodium atom is extremely crucial for this, explains Thomas Zeuch, as it allows the clusters of the desired size, i.e. the 275 water molecules, for example, to be gently ionized, sorted with an electric field and measured specifically.
Udo Buck developed the fundamental principle of the experiment at the Max Planck Institute for Dynamics and Self-Organization. Today, the apparatus is with Thomas Zeuch at the University of Göttingen. The scientists in this group had theoretical support from Prague as they continued to develop it until it became possible to investigate clusters comprising several hundred water molecules. The researchers now want to experimentally investigate the crystallization of further substances and their surface properties as well – accurate to one molecule, where possible. Another reason why Zeuch is so enthusiastic about the new experimental procedure is that it can be applied not only to water clusters. It opens up a completely new field of experimentation.
1 Comment on "Forming the Smallest Ice Crystals in the World"
It is my belief that the crystal is a representative structure of the quantum length of the element or combining elements that determine the location of each point and axies.. If you imagine that every discreet quanta, or element is of a certain size. The size of the combining spheres deterinines where the intersecting points of the structure will be, and there are 2 apexs's for each circle which would say that an irrational number cannot exist, order is maintained by magnetic equalibrium of orbits.The very reason superconductors work is because of disimilar structures, close enough to bond yet just barley.. the excentric is what allows unresricted electron flow.