sabato 13 ottobre 2007

Quantum Mechanics Predicts Unusual Lattice Dynamics Of Vanadium Metal Under Pressure


Science Daily — A Swedish research team of Dr. Wei Luo & Professor Rajeev Ahuja and US team of Dr. Y. Ding & Prof. H.K. Mao have used theoretical calculations to understand a totally new type of high-pressure structural phase transition in Vanadium. This phase was not found in earlier experiments for any element and compound. These findings are being published in the Proceedings of the National Academy of Science.
The relation between electronic structure and the crystallographic atomic arrangement is one of the fundamental questions in physics, geophysics and chemistry. Since the discovery of the atomic nature of matter and its periodic structure, this has remained as one of the main questions regarding the very foundation of solid systems.
Scientists at Carnegie's Geophysical Laboratory, USA and Uppsala University, Sweden have discovered a new type of phase transition - a change from one form to another-in vanadium, a metal that is commonly added to steel to make it harder and more durable. Under extremely high pressures, pure vanadium crystals change their shape but do not take up less space as a result, unlike most other elements that undergo phase transitions. This work was appeared in the February 23, 2007 issue of Physical Review Letters.
Trying to understand why high-pressure vanadium uniquely has the record-high superconducting temperature of all known elements inspired us to study high-pressure structure of vanadium. Usually high superconductivity is directly linked to the lattice dynamics of material.
In present paper in PNAS, again a collaboration between Uppsala University and Carnegie's Geophysical Laboratory, USA, we have looked in to the lattice dynamics of vanadium metal and it shows a very unusual behavior under pressure.
A huge change in the electronic structure is driving force behind this unusual lattice dynamics. Moreover, our findings provide a new explanation for the continuous rising of superconducting temperature in high-pressure vanadium, and could lead us to the next breakthrough in superconducting materials.
Note: This story has been adapted from material provided by Uppsala University.

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