Molecular Mobility in Crystals
- Kanina Foss
Demetrius Levendis delivers inaugural lecture after becoming full Professor in the School of Chemistry.
Professor Demetrius Levendis delivered his inaugural lecture to an audience of friends, family and colleagues on Tuesday, 28 October 2014.
The lecture took place four years after Levendis was made a full professor in the School of Chemistry at Wits University, but since the title of the lecture was: Molecular Mobility in Crystals, and since 2014 is the International Year of Crystallography, the timing could not have been better.
According to Levendis, the International Year of Crystallography commemorates 100 years of the study of crystals by x-ray diffraction, and the magnificent contribution that this has made to science, which is often not recognised.
Crystallography is the study of crystals. Although it does not involve only x-ray diffraction, it has become synonymous with x-ray diffraction, which involves shining x-rays on crystals to produce a periodic pattern, used to deduce the crystal structure, or the position of the atoms.
The word “crystallography” comes from the Greek word “krustallos” which means ice. The ancient Greeks believed that all crystals were some form of ice. In fact, we are still debunking myths about crystals today, as was demonstrated by Lenvendis who used his lecture to reveal some interesting facts about the way that molecules in crystals can be seen to move.
“Crystals are generally considered to be rigid, so the atoms of the molecules don’t move at all; they’re considered to be periodic, so you’ve got a repeating pattern that occurs in all three dimensions; and they’re considered to be inert, so if you’ve got a crystal and you heat it up or expose it to light, it doesn’t react,” said Levendis.
Taking his line from fellow South African chemist, Jan Boeyens, who said that it was necessary to treat the contents of all textbooks with suspicion, Levendis used four different crystal systems to illustrate how crystals could – contrary to the view that they are rigid, periodic and inert – demonstrate molecular mobility.
Listen to his full lecture: