Harald Franzen
Scientific American
A
new kind of nitrogen is what researchers at the Carnegie Institution of Washington
have created by applying immense pressure to ordinary nitrogen gas. Their findings
are published in this week's issue of Nature.
Nitrogen gas (N2) is abundant
on earth, making up about 75 percent of the planet's atmosphere. The triple bond
between the two nitrogen atoms makes the gas a very stable compound. At low pressure
and temperature, nitrogen forms molecular crystals and becomes an electric insulator.
But scientists predicted that by raising the pressure on these crystals to 50
to 94 gigapascals, the nitrogen molecules could be transformed into monoatomic
metallic solids. (One gigapascal is roughly 10,000 times the atmospheric pressure
experienced at sea level.)
The researchers not only managed to create
such solid nitrogen but also found that, unlike its molecular crystal predecessor,
the nitrogen becomes a semiconductor in this state. Moreover, they managed to
keep the nitrogen in solid form after lowering the pressure back down to normal
levels (at temperatures below 100K). "The fact that the major portion of the air
has been turned into a semiconducting solid and brought back to be stable at ambient
pressure is an important breakthrough for us," team leader Russell Hemley says.
The results of this study confirmed theories that were used to predict
new properties, such as high-temperature superconductivity in metallic hydrogen.
The researchers initially wanted to convert hydrogen in this manner and they hope
to eventually do so. |
