Transcript Slide 1

The Formation of Ice VI Under Static Pressure
1
Ploeg ,
2,3
McCluskey ,
2,3
Hanna
H.K.
M.D.
G.J.
1The University of Michigan, Ann Arbor, MI
2 Institute for Shock Physics, Washington State University, Pullman, WA
3Dept. of Physics and Astronomy, Washington State University, Pullman, WA
Phase Change:
Procedure:
•Starting from ambient pressure, keeping the temperature constant at 294 K, the pressure is
slowly increased until a phase change is observed at about 9.8kbar.
•The phase diagram (left) confirms that the cell contains ice VI.
•The entire sample freezes to ice VI in under a second; after the phase change the sample
appears the same as before.
•Reducing the pressure melts the sample; melting takes about 90 minutes.
Water Becoming Ice VI:
The ice begins to form on the outer ring of
the sample and progresses towards the
center. The entire sample is converted to ice
VI in less than a second (right). The ruby
chip is visible in the upper left of the sample.
t=0
t = 0.04 s
0.66 mm
t=0
t = 0.04 s
t = 81 s
t = 0.17 s
The diamond anvil cell is
illustrated below. Because the
diamonds have a small contact
area, a small force creates a
very large pressure. Turning
the screws on the cell
increases the pressure on the
sample. The sample consists
of water and a small ruby chip
for measuring the pressure.
The metal gasket enclosing the
sample is made of beryllium
copper. (The anvils used in this
experiment are actually
moissanite.)
t = 0.67 s
Ice VI Becoming Water:
t = 921 s
t = 1521 s
The first slide is solid ice VI
at a pressure near 10kbar.
After the pressure is slowly
released the ice cracks and
the phase change begins.
The pressure continues to
drop inside the gasket. The
ice breaks up into smaller
pieces that coalesce into
larger ones, but the total
mass of the ice gets smaller.
Eventually only liquid water
remains.
Citations:
M. Chakroun and O. Grasset, Journal of
Chemical Physics 127, 124506 (2007)