Under extremely high pressure, sodium—an
excellent conductor—turns into a transparent insulator.
Micromillimetre-sized samples of sodium were subjected
to a pressure of two million atmospheres. The overlapping
of sodium atoms forced the outer electrons to go into
spaces between the atoms. This led to a collapse of its
metallic state while its colour changed from black to
red to transparent. This find defies existing knowledge
that says under high pressures an element goes metallic.
The findings, published in the March 12 issue of Nature,
will help understand the properties of highly compressed
matter found in stars and giant planets.
