Oct 14 2008
An international research team led by Professor Rajeev Ahuja, Uppsala University, has used theoretical calculations to understand a high-pressure structural phase transition in silane which could gives rise to metallization and could even result in superconductivity. The findings are published this week in the online edition of the Proceedings of the National Academy of Sciences of the United States of America (PNAS).
Hydrogen is the the one of most abundant and lightest element in the universe, and it has been speculated already fifty years back that metallization in pure hydrogen could lead to room- temperature superconductivity, which has been an open question till now. But enormous pressure would be required to compress hydrogen sufficiently in order to achieve this metallic state. One way to overcome this problem is to take advantage of so-called “chemical pressure”, generated by introducing other elements, such as silicon, to exert additional pressure by “sandwiching” the hydrogen layers, producing a hydrogen-rich material known as silane.
Earlier this year, experimentalists at the Geophysical Laboratory of the Carnegie Institution of Washington have reported on the metallization of silane under pressure, but it remained unclear in what crystal structure silane existed in these experiments.
This prompted the team led by Professor Rajeev Ahuja to carry out a systematic computercomputational experiments based on state-of-the-art first-principles methods to determine the structure for metallic silane, and they succeeded in identifying one crystal structure from a pool of plausible candidates that matches all requirements. The findings are in excellent agreement with experiment and allowed even for the prediction that the metallic phase of silane could exist at lower pressures. The extensive simulations were performed at Uppsala University’s Multidisciplinary Center for Advanced Computational Science (UPPMAX).
"Metallization of silane represents an extraordinarily important discovery”, says Professor Rajeev Ahuja. “Our results can be seen to represent an important advancement in the theoretical search for metallic and even superconducting hydrogen within a tractable pressure regime."