POSSIBLE PHASE TRANSITION IN H2O ICE Ih NEAR 110 K
David T. W. Buckingham
Sueli H. Masunaga
Forrest C. Gile
John J. NeumeierNSF AWARD DMR-1204146
W12.07:
MOTIVATION We observed a phase transition in thermal expansion measurements of H2O ice Ih.
Structural understanding of transition glassy crystal [1].
: Heat capacity of ice divided by
temperature vs
temperature.
Samples were
subject to
different thermal
treatments. [1].
[1] Haida, O., et al., Calorimetric Study of the Glassy State X. Enthalpy Relaxation at the Glass-Transition Temperature of Hexagonal Ice,
J. Chem. Thermodynamics, 6, 815 (1974)
: Thermal expansion
coefficient of ice
vs temperature
measured along
a- and c-axes.
Inset shows
percent-change
in length at 5 K.
SLOW & DISORDERED ICE Ih
Total number, , of allowed (ice rules)
hydrogen configurations within crystal of
molecules [2]:
= 61
2
2
=3
2
Giving rise to zero-point entropy,
0 = ln3
2= 3.371 J K1 mol1
[2] Pauling, L., The Structure and Entropy of Ice and of Other Crystals with Some Randomness of Atomic Arrangement, J. Am. Chem. Soc., 57, 2680 (1935)
: The six possible orientations of hydrogen configuration around an oxygen
atom. p shows direction of electric dipole
moment of first orientation.
[3] Suga, H., Ultra-Slow Relaxation in Ice and Related Substances, Proc. Japan Acad., 81, Ser. B (2005)
: Hexagonal crystal structure of ice. Tetrahedral bonding and hexagonal
structure force highly disordered proton
configuration.
SLOW & DISORDERED ICE Ih
Total number, , of allowed (ice rules)
hydrogen configurations within crystal of
molecules [2]:
= 61
2
2
=3
2
Giving rise to zero-point entropy,
0 = ln3
2= 3.371 J K1 mol1
[2] Pauling, L., The Structure and Entropy of Ice and of Other Crystals with Some Randomness of Atomic Arrangement, J. Am. Chem. Soc., 57, 2680 (1935)
: The six possible orientations of hydrogen configuration around an oxygen
atom. p shows direction of electric dipole
moment of first orientation.
: The dielectric relaxation time of pure H2O ice Ih. Suga [3] used calorimetry and
dielectric measurements.
[3] Suga, H., Ultra-Slow Relaxation in Ice and Related Substances, Proc. Japan Acad., 81, Ser. B (2005)
THERMAL EXPANSION EXPERIMENT Capacitance-based fused quartz dilatometer [4].
Resolution:
Absolute, ~0.1 .
Relative, 10-9.
Ultrapure Milli-Q H2O = 18.2 @ 25 ,
deaerated in vacuum, zone-refined single crystals [5].
Crossed-polarized light orientation.
Measured on warming, 0.2 K/min.Vlowering < 0.4 cm/day
: Exploded view of dielectric cell.
: Assembled dielectric cell with
non-ice sample (black
piece).
: Ice samples viewed between crossed-polarizing filters. Quarter
is for size scale.
: Cross-section of single crystal growth apparatus.
[4] Neumeier, J. J., et al., Capacitive-Based Dilatometer Cell Constructed of Fused Quartz for Measuring the Thermal Expansion of Solids, Rev. Sci. Inst., 79, 033903 (2008)
[5] Bilgram, J., et al., Perfection of Zone Refined Ice Single Crystals, J. Crystal Growth, 20, 319 (1973)
16
cm
THERMAL EXPANSION RESULTS Transition in thermal expansion
coefficient, , of magnitude
105 K1 near 110 K as
measured parallel to c-axis.
No such transition as measured
parallel to a-axis.
Increase of transition
temperature, , with increase in
cooling rate.
Figure: Thermal expansion
coefficient versus temperature.
Inset shows the cooling rates of
each measurement.
Figure: Capacitance versus time. Each curve was measured at constant
temperature (5 mK).
DIELECTRIC RELAXATION EXPERIMENT
Dielectric cell made of fused quartz with Au
electrodes, BeCu springs.
Measure charge versus time at constant temperature
(5 mK) from 102 149 K.
Fit data with equation for charging capacitor:
= 1
At = 5, capacitor is 99.3% charged net dipole
moment has reached 99.3% of its maximum.
5 = dielectric relaxation time.
: Dielectric cell with ice
sample as
dielectric.
c-axis
Figure: Dielectric relaxation time versus temperature as measured by
Suga [3] and our saturated capacitance measurements.
DIELECTRIC RELAXATION EXPERIMENT
Dielectric cell made of fused quartz with Au
electrodes, BeCu springs.
Measure charge versus time at constant temperature
(5 mK) from 102 149 K.
Fit data with equation for charging capacitor:
= 1
At = 5, capacitor is 99.3% charged net dipole
moment has reached 99.3% of its maximum.
5 = dielectric relaxation time.
: Dielectric cell with ice
sample as
dielectric.
THERMALLY STIMULATED DEPOLARIZATION (TSD) CURRENT
Cool sample (0.2 K/min) in electric field. Remove
field, measure current on warming (0.2 K/min).
Molecular dipole relaxation results in release of
charge from capacitor plates current peak.
Anisotropy indicates different relaxation processes
along crystallographic axes.
Circuit diagram for TSD measurement. V=550V is
applied DC voltage, S a
switch, C is capacitor with
ice as dielectric, G the
capacitor guard ring, A the
ammeter.
TSD current versus temperature measured after electric field was applied parallel to (red) and perpendicular to (blue) the c-axis.
DEPENDENCE ON COOLING/WARMING RATE
Recall shift in dependent on
cooling rate.
DEPENDENCE ON COOLING/WARMING RATE
Recall shift in dependent on
cooling rate.
Johari & Jones observed a shift in TSD current
peak(s) near 110 K in pure polycrystalline ice
when measured with different warming rates [6].
Argue ice Ih undergoes a relaxation
phenomenon frozen-in proton configuration
relax at different T depending on warming rate.
No knowledge regarding anisotropy of effect.
[6] Johari, G. P. and Jones, S. J., Study of the Low-Temperature Transition in Ice Ih by Thermally Stimulated Depolarization Measurements, J. Chem. Phys., 62, 4213
(1975)
Figure: TSD current of pure ice
measured with different
warming rates
CONCLUSION & FUTURE WORK Transition in thermal expansion coefficient of H2O ice Ih:
Anisotropic
Glass transition associated with the freezing-in of the proton configurations.
Verified by residual entropy, s dependence on cooling rate and TSD current.
Future plans:
Measure potential anisotropy in dielectric relaxation time.
D2O and KOH-doped ice thermal expansion and dielectric properties.
THANK YOU!
QUESTIONS?