Pressure calibration is a central technical challenge of highpressure research that

1
Pressure calibration is a central technical
challenge of high-pressure research that goes
hand in hand with experimental advances. Scient
ific Questions Transition zone seismic
discontinuities 410, 660 km depth Clapeyron
slope connection to geodynamics Core-Mantle
boundary Depth of pPv transition Phase
transition vs chemical/thermal boundary Chemical
composition (e.g. Fe) Clapeyron slope Triple
point, melting curve of H2O Equation of state
parameters sensitive to P calibration (e.g.
diamond, Fe)
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What are some things we have learned? Ruby
Scale Ruby scale is in need of revision gt50
GPa -- definitely 0-50 GPa perhaps Open
Questions Inconsistency of shock
standards Can we improve shock thermal
corrections? Static studies of Au are not in
agreement Emphasizes need for
redundancy Details of loading, sample
environment may matter Strength of He?
3
Absolute pressure scales from
elasticity/volume data highly promising Open
questions? Careful analysis of effects of
adiabatic/isothermal corrections What is
limitation due to our inability to measure K to
high precision? MgO K 3.8-4.2 -- 10
uncertainty What are P-T limits of such
measurements?
4
Pressure at high temperatures New optical
sensors cBN, diamond X-ray
markers Thermal equation of state First
principles theory, new semi-empirical EOS models
Open questions How accurate are our
temperature determinations?
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Open Questions (contd) Thermal equation of
state remains one of the most challenging and
unsolved technical questions Within framework
of Mie-Gruneisen-Debye EoS LVP -- sensitive to
?0, not q DAC -- Strong tradeoff between K, K
and q Best functional form of the thermal
equation of state? Mie-Gruneisen-Debye Thermod
ynamic consistency Gibbs energy Anharmonicity
How do we best incorporate first principles
theory? Very powerful insights that cannot be
obtained from exp. Inherent approximations
prevent direct use Simplicity vs Completeness
number of parameters 6-22
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What do we need to do (both individually and as a
community)? Communication and
Education Special issue of High-Pressure
Research AIRAPT, Shock/Static joint
conference COMPRES Main impetus comes from
individual investigators Spirit of openness
and cooperation Do we need to establish a
database of static compression data? examples
Shock compression database, Am. Min. crystal
structure database volume, pressure,
pressure scale of publication ability to
convert data to any other pressure scale for a
given standard
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Proposed experimental program (COMPRES
development project?) Fundamental
thermoelastic/shock data for simple metals are
essential Shock data mostly obtained in
1950-1970s Ultrasonic elasticity data (K, K)
1950-1970s Peak pressure 1 GPa Bulk Modulus
contrained to better than 1 Pressure
derivative of K (K) gt10 variation Example
P derivs. of Cijs for Pt not measured. Project
Program to characterize elasticity of Au, Pt,
Mo, Ta, Cu, Al, and Ag at high P and T New
elasticity techniques Impulsive stimulated
scattering in DAC Inelastic xray scattering in
DAC ultrasonic elasticity in large volume press