New research could help scientists unravel some of the mysteries concerning the hot iron core of Earth. Image: NASA. |
Conventional scientific
wisdom says that the interatomic forces between ions that control
high-temperature processes such as melting are insensitive to the heating of
the electron “glue” that binds the ions together. In effect,
traditional atomistic simulations ignore electron temperature completely.
However, in Physical
Review Letter, Lawrence Livermore National Laboratory (LLNL) physicists
John Moriarty, Randolph Hood, and Lin Yang show how electron temperature has a
surprisingly large impact on phase stability and melting in refractory
transition metals like molybdenum, where the binding d electrons form strong
directional bonds.
The LLNL team has
developed a new atomistic simulation capability to treat such effects quantum
mechanically through temperature-dependent, multi-ion interatomic potentials
that can be used in large-scale simulations of thermodynamic and mechanical
properties of materials.
This capability could
help scientists unravel phase-diagram mysteries concerning the hot iron core of
the earth as well as help engineers design safer nuclear reactors.
In the past decade,
high-pressure melting of transition metals and the possibility of undiscovered
stable solid phases just below the melting temperature have been subjects of
widespread scientific interest, as well as considerable controversy.
“The present advance
not only sheds new light on such high-pressure phase-diagram issues, but it
will also enable in-depth investigations of other important problems in
high-temperature materials science,” Moriarty said.
These problems include
the design of improved high-temperature alloys for jet engines, the mitigation
of stress-corrosion cracking in nuclear reactors, and the accurate modeling of
ultra-fast laser-heating experiments performed on facilities like the National
Ignition Facility (NIF), in which the electrons are rapidly heated far above
the ion temperature, altering normal materials properties.
