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| Yonezawa has been teaching theoretical physics at Keio University since 1983 (1984). |
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Physics deals with the properties of various types of
matter. The topic I studied for many years was the properties of amorphous
solids--that is, solids that are not crystalline in structure. When most
people hear the word crystal, they think of snowflakes or quartz
crystals. But actually, almost all the matter around us is either crystalline
in structure or a mixture that includes crystalline solids. Amorphous solids
are less common, but one with which everyone is familiar is glass, which
is made out of quartz and sodium carbonate.
At high temperatures, the atoms of which matter is made move around energetically,
and their arrangement becomes random and disordered. But when this matter
cools slowly and becomes solid, the atoms arrange themselves in a regular
pattern. The way to create amorphous solids, in which the atoms are randomly
arranged, is to cool matter very rapidly from a high temperature. I wanted
to see with my own eyes what happened when materials cooled at different
rates, so I created computer simulations to show the process. It turns out
that as long as the conditions are right, any substance can be made amorphous,
but with metals, which crystallize especially easily, we use special methods,
such as cooling them while spinning them rapidly.
In a virtual experiment using computer graphics, we cooled argon at a rate
of 400 billion degrees per second. When we calculated the movement of 864
atoms every 5/1015 second (or 5 femtoseconds) we saw here and there atomic
structures that block crystallization. This kind of experiment can only
be done with a computer, since it's impossible to cool substances that fast
in the laboratory. |
