Approaches to Educational Technology

The definition of crystals had to be changed after the 1984 discovery of quasicrystals by the Nobel Laureate Dan Shechtman. Photo: R. Prasad

Unlike religion, science is not dogmatic and is open to revision. “But in the frontiers of science there is not much of a difference between science and religion,” said Nobel Laureate Dan Shechtman.

Prof. Shechtman is from Technion — Israel Institute of Technology, Haifa, Israel. “People have their beliefs and they would not listen.”

But is that how science should be? “You are absolutely correct. Science should not be this way, because sometimes people are wrong,” the Laureate said. “A good scientist is a humble person who is willing to listen and not somebody who thinks he knows everything.”

Prof. Shechtman won the Nobel Prize for chemistry last year for his 1984 discovery of quasicrystals (non-repeating regular patterns of atoms). He had used a transmission electron microscope (TEM) to study the quasicrystals.

“When I published my work many repeated my results and immediately said, hey, we have it,” he said.

His personal experience convinced him that in the frontiers of science there is little difference between science and religion. “It was a discovery challenging a community of X-ray crystallographers. They were really against me for ten years,” he noted.

The science of crystallography was defined as X-ray crystallography. Hence all results were to be obtained using X-rays and nothing else. “This community of X-ray crystallographers wanted him to get X-ray diffraction results” before they could accept his results.

It took his team three years (from 1984 to 1987) to produce the first large enough crystal that is fraction of a millimetre in size. “Only then we could get an X-ray diffraction pattern” he said. The X-ray crystallographers finally accepted his results when he finally presented the X-ray diffraction results at a meeting in Australia. “They redefined crystals. This was a paradigm shift,” he said.

According to a press release from the Royal Swedish Academy of Sciences , quasicrystals “fundamentally altered how chemists conceive of solid matter.”

According to the classical definition, crystals can have rotational symmetries of one, two, three, four and six. Five-fold symmetry and symmetries beyond six were thought to be impossible in periodic structures.

The atoms inside a crystal have to necessarily be packed in a symmetrical pattern so that they are ordered and repeated periodically. But quasicrystals meet only one of the two conditions — they are ordered materials, but the atomic order is quasiperiodic rather than periodic. It is this combination that allows the formation of crystal symmetries, such as icosahedral symmetry.

Talking about tenacity, he recalled his struggle. “I experienced severe criticism for ten long years,” he said. Those who opposed his results were not experimentalists, and the reason for opposing them was not on scientific grounds. “This cannot be [correct], they said. ‘But this cannot be’ was not based on the second law of thermodynamics but was based on a paradigm,” he said. After all, hundreds of thousands of crystals were studied before and not one of them turned out to be a quasicrystal.

But Prof. Shechtman took the road less travelled and used a TEM to study quasicrystals. These cannot be found using X-ray diffraction (unless they are grown to at least a fraction of a millimetre) as they are so small. “So the question is why didn’t others see it before I did. It is not because it is not stable or rare or difficult to make,” he asked.

Using a different tool is only the beginning. “It is not enough to operate a TEM. You must be an expert on TEM. The number of TEM experts is very few,” he said.

But when he finally observed quasicrystals he did not understand their significance. “I thought what I saw was just an artefact caused by twins. So I was looking for twins that have boundary between crystals giving mirror images. I did not find it and I knew I did not have twins,” he recalled. “Everything happened in just one day on April 8, 1982.”

Quasicrystals have low heat conductivity and non-stick properties. “It is better than Teflon as it does not stretch,” he said.

(This Correspondent is one of the two journalists from India participating in the 62ndNobel Laureates Meeting at Lindau, Germany, at the invitation of the German Research Foundation (DFG) Bonn.)

Keywords: Lindau Nobel Laureates Meeting, Nobel Laureates, Dan