Squeezed hydrogen turns semi-metallic.Squeezed hydrogen turns semi-metallic
For years, scientists have tried compressing hydrogen until it becomes a metal. Current theory predicts that a sufficiently large In mathematics, the phrase sufficiently large is used in contexts such as:
Process by which nuclear reactions between light elements form heavier ones, releasing huge amounts of energy. In 1939 Hans Bethe suggested that the energy output of the sun and other stars is a result of fusion reactions among hydrogen nuclei. .
Now, two scientists from the Carnegie Institution of Washington The introduction to this article may be too long. Please help improve the introduction by moving some material from it into the body of the article according to the suggestions at in Washington, D.C., report seeing the first glimmer of their long-awaited goal. Ho-Kwang Mao Ho-Kwang (Dave) Mao is a staff scientist at the Geophysical Laboratory of the Carnegie Institution of Washington. He is one of the most prolific users of the diamond anvil cell for research at high pressures. and Russell J. Hemley observed changes in their hydrogen samples indicating that, if not already metals, these samples have at least reached an important intermediate state as semiconductors, or semi-metals. They presented their finding earlier this month at the American Geophysical Union The American Geophysical Union (or AGU) is a nonprofit organization of geophysicists, consisting of over 50,000 members from over 140 countries. AGU's activities are focused on the organization and dissemination of scientific information in the interdisciplinary and meeting in Baltimore.
The researchers achieve a pressure comparable to that near the center of the earth by squeezing materials between two gem-quality diamonds in a "diamond anvil anvil
Iron block on which metal is placed for shaping, originally by hand with a hammer. The blacksmith's anvil is usually of wrought iron (sometimes of cast iron), with a smooth working surface of hardened steel. ." The device works by concentrating a force over a small area, the way a high-heeled shoe painfully concentrates a person's weight on a stepped-on toe.
Ten years ago, Mao and Peter M. Bell used the diamond anvil to compress hydrogen into a new kind of crystalline solid at 1.7 megabars, or 1.7 million times atmospheric pressure (SN: 3/10/79, p.156). Now they can reach 2.5 megabars. At this pressure, when the researchers peer through the transparent diamonds, they see the hydrogen turn opaque. This indicates the sample is becoming metallic, explains Mao, because electrons of semiconductors and conducting metals absorb visible light. The team cannot yet test the sample directly for electrical conductivity, but Mao says they expect to eventually develop this capability.
Mao and Hemley say they have little idea what metallic hydrogen might be like -- it could even be a liquid. Their work should improve scientists' understanding of the planets Jupiter, Saturn, Uranus and Neptune, which may have metallic-hydrogen cores. In addition, the possibilities of a superior superconductor or a new fusion source remain open. While fusion efforts have failed to produce more energy than put in, Mao says, a more compact hydrogen starting material could help boost efficiency.