differ from crystals. Crystals are organized in repeating patterns that
extend in every direction. Glasses lack this strict organization, but
do sometimes demonstrate order among neighboring atoms. New research
from Carnegie’s Geophysical Laboratory reveals the possibility of
creating a metallic glass that is organized on a larger scale. Their
results are published June 17 in Science.
have discovered glasses that demonstrate order among the nearest
neighboring atoms, called short-range order, and a slightly wider range
of atoms, called medium-range order. Most research about finding or
creating a glass with a long-range, nearly crystalline, level of
order—referred to as the perfect glass state—has been conducted on ice
and the minerals silica and zeolite. But no research into long-range
order glass has been successful until now.
research team, including Carnegie’s Ho-Kwang (Dave) Mao, focused on
metallic glass made from the elements cerium and aluminum. Metallic
glasses are a hot research topic, because they are less brittle than
ordinary glasses and more resilient than conventional metals. They
combine the advantages and avoid many of the problems of normal metals
and glasses, two classes of materials with a very wide range of
placing the cerium-aluminum glass under 25 gigapascals of
pressure–about 250,000 times normal atmospheric pressure–the team was
able to create a single crystal. When the glass was brought back to
ambient pressure, the new structural order was preserved.
x-ray techniques and simulations, the team determined that the atomic
structures of cerium and aluminum prevent the glass from assuming the
highly ordered state at normal pressures. But under the intense 25
gigapascals, an electron in cerium shifts, allowing the crystalline
structure to be created.
exciting results demonstrate that pressurized cerium-aluminum glass
could be a favorable system for discovering the long-sought-after
perfect glass,” Mao said. “This situation could also exist in other
for this research was provided by the U.S. Department of Energy Energy
Frontier Research Center, The use of HPCAT, APS is supported by Carnegie
Institution for Science, Carnegie DOE Alliance Center, University of
Nevada at Las Vegas and Lawrence Livermore National Laboratory through
funding from DOE-National Nuclear Security Administration, DOE-Basic
Energy Sciences, and NSF. The TEM measurements were conducted at the
Electron Microscopy Center at ANL. Computational work was supported by
NSF and conducted on the supercomputing system supported by the Center
for Computational Materials Science, Tohoku University. The SLAC effort
is supported by DOE.