D. L. Decker

High‐Pressure Equation of State for NaCl, KCl, and CsCl

A calculation of the equation of state for NaCl from a Mie‐Gruneisen equation was repeated using more accurate values of the zero‐pressure compressibility. It was also extended to KCl and CsCl. An analysis of this approach to pressure calibration indicates that it will yield pressures with about the same accuracy as can be presently achieved by experimental measurements above 25 kbar, and thus furnishes a temporary practical pressure scale.

Equation of State of NaCl and Its Use as a Pressure Gauge in High‐Pressure Research

The pressure as a function of lattice parameter and temperature has been calculated for NaCl over a pressure range of 0 to 500 kbar for temperatures between 0° and 1500°C. The calculation used the Mie‐Gruneisen equation of state with Born‐Mayer type repulsion terms between first and second nearest neighbors. The Gruneisen constant was expanded about its value at room temperature and atmospheric pressure; the first coefficient in the expansion being evaluated by forcing the calculated thermal expansion at atmospheric pressure to fit the experimental results of Enck. The two empirical parameters in the repulsion terms were evaluated using the experimental lattice parameter and isothermal compressibility at atmospheric pressure. The calculated pressure vs volume agrees with Bridgmans room‐temperature measurements in NaCl below 100 kbar to within 3% and with high‐pressure high‐temperature shock data to better than 2%. It is proposed to use the numerical results to calibrate the pressure in high‐pressure high...

High‐Pressure Calibration: A Critical Review

A critical review of experimental technique for measuring high pressures has been made. The broad coverage includes discussions relating to (a) the establishment of a primary pressure scale using the free‐piston gage, (b) the selection and precise measurement of identifiable phase changes as fixed pressure points, and (c) the use of interpolation and extrapolation techniques such as resistance gages, equations of state, and optical changes. The emphasis is on static pressure measurements above 10 kbar, but shock measurements are also considered for completeness. The pressure values to be associated with the fixed points have been analyzed in detail. Temperature measurement in the high pressure environment is also reviewed. The accuracy with which pressures can be measured has been carefully considered; the maximum accuracies now obtainable are considered to be of the order of 0.02 percent at 8 kbar, 0.25 percent at 25 kbar, 2 percent at 50 kbar, and 4 percent at 100 kbar.

Equation of State of Sodium Chloride

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Proposed Thermodynamic Pressure Scale for an Absolute High‐Pressure Calibration

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Multicomponent profile refinement of time-of-flight neutron diffraction data☆

Abstract Methods of profile analysis of time-of-flight neutron diffraction data containing contributions from several materials have been developed and have been used to fit patterns obtained from materials under high pressure. Several hundred diffraction lines from up to four different materials can be analyzed simultaneously. The analysis yields the atomic positions, lattice parameters, temperature factors, preferred orientation parameters, and scale factors directly from fitting the raw data. The scale factors can be used to estimate the percentages of each component contributing to the pattern.

Structure of high-pressure KNO3-IV*

Potassium nitrate has seven polymorphs in the pressure range to 40 kbar. The structures of the three phases obtainable at atmospheric pressure are known. Attempts to solve the structure of high pressure KNO3 phase IV by X-ray diffraction have been unsuccessful. We have now solved this structure using time-of-flight neutron powder diffraction data taken at room temperature and 3.6 kbar on the SEPD at IPNS. High pressure KNO3-IV has the same space group and point group symmetry as the low pressure KNO3-II, but with different values for lattice parameters and atomic positions. The structure of KNO3-IV is orthorhombic Pnma with a = 7.4867(2), b = 5.5648(2), and c = 6.7629(2) with four formula units per unit cell. The K, N, and one O atom are in special positions (4c) and the other O atoms are in the general position (8d) just as in the atmospheric pressure phase. The O-N-O bond angles are 120.4(1)°, and 119.3(2)°. The N-O bond lengths are 1.228(3) A and 1.246(2) A.

Anomalous nuclear reactions in condensed matter: Recent results and open questions

We have observed clear signatures for neutron emission during deuteron infusion into metals, implying the occurrence of nuclear fusion in condensed matter near room temperature. The low-level nuclear phenomenon has been demonstrated in collaborative experiments at Brigham Young University, at the Gran Sasso laboratory in Italy, and at the Los Alamos National Laboratory. We have shown that neutron emission can be induced in metals using both electrochemical and variational temperature/pressure means to generate non-equilibrium conditions. Observed average neutron emission rates are approximately 0.04–0.4 no/s. Current efforts focus on trying to understand and control the phenomenon. In particular, we wish to understand the correlation of neutron yields with parameters such as hydrogen/metal ion ratio, pressure (induced, for example, by electrical field or gas pressure or mechanical pressure), temperature variation, hydride phase changes, and surface conditions, e.g., a palladium coating on titanium. We want to know if fusion arises due to the close proximity of the deuterons in the lattice (piezonuclear fusion), or possibly from “microscopic hot fusion”, accompanying strong electric fields at propagating cracks in the hydride. The latter interpretation would imply neutron emission in bursts. Our experiments show clear evidence for emission of ∼102 neutrons in bursts lasting <128 μs, although random neutron-singles emissions were also observed. Experiments now underway to compare thed−d, andp−d, andd−t reaction rates will be important to a consistent description of the new phenomenon. Careful scrutiny of this effect could increase our understanding of heat, helium-3, and tritium production in the earth, other planets, and even the stars.

Mössbauer measurements on iron at high pressure and elevated temperatures

Abstract Mossbauer spectra near the triple point of iron are compared for ferromagnetic α iron and non magnetic ϵ and γ iron. The isomer shifts from α to ϵ and γ iron are −0.096 ± 0.007 and −0.014 ± 0.019 mm/sec respectively.

Surface conductance of a copper wire in a fluid at high pressure

The three‐dimensional flow of heat in a wire carrying a current and immersed in a liquid is solved in detail. Using this exact result the surface conductance of copper in petroleum ether has been measured as a function of pressure to 40 kbars. The measured surface conductance for copper in a fluid is very small, justifying approximations which yield results that are in agreement with a simplified one‐dimensional heat‐flow problem. Surprisingly, even at 40 kbars pressure a very large fraction of the joule heating within a wire with a length‐to‐diameter ratio of ∼100 is dissipated through the ends of the wire rather than to the surrounding liquid.