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Nitrogen Semiconductors
wearedan writes: "I came across an article on how nitrogen acts as a semiconductor when under very high pressures.The really interesting bit is that the formed solid can be stable even when returned to ordinary atmospheric pressures."
Anyone know what they used to achieve such high levels of atmospheric pressure?
For the metallic hydrogen experiments I read about a while back, they used a "diamond anvil cell". This is a fairly small device that uses a screw to close a pair of lever arms. The compression cell at the base of the lever squeezes the sample between two diamonds. A metal gasket surrounds the cell.
The nice thing about this is that the diamonds pass a wide range of light frequencies, which lets you measure material properties optically.
The group that I was reading about almost, but didn't quite, succeed in making metallic hydrogen.
I have no idea whether the nitrogen semiconductor group used this apparatus or something else. I suppose that if you were clever enough to find a fast way to take the measurements, you could just set off a bomb on top of the sample and measure for a few microseconds. Pressure is difficult to control, but if you can measure pressure accurately while you do this, you can simply plot your data with pressure as one of the axes.
Some types of industrial diamond are made using explosives.
Just wondering, when it returns to normal preasure levels, they apparenlty have this new substance remaining after it forms at high preassure. Is there any chance of it returning to a gasous form and hence exploding to it's original volume?
Sure. Just heat it. It's both more entropically favourable and more energetically favourable for it to be a gas (above nitrogen's freezing point, at least), so as soon as you get over the activation energy, *boom*.
According to the article, the sample at 1 atm had to be cooled quite a bit to be stable. For all I know, they could have taken it down below nitrogen's freezing point, which would just make this an interesting allotrope of frozen nitrogen.
Material properties should change as pressure is varied, as the energy bands within the material will shift. This would be very interesting to measure experimentally to check our models of materials at high pressures (and you can bet your socks they've submitted a funding application already to do this).