Thermodynamic evaluation and optimization of the (NaCl + KCl + AlCl3) system

All available phase equilibrium and thermodynamic data for the (NaCl + KCl + AlCl₃) system were collected and critically evaluated. An optimization was performed to obtain the parameters of one set of model equations for each phase (solids, liquid, gas) in order to best reproduce all the data simultaneously. In this way the data are rendered self-consistent, discrepancies among the data are identified, and extrapolations and interpolations can be performed. For the molten phase the Modified Quasichemical Model for short-range ordering was used, with monomeric Al³⁺ ions (corresponding to AlCl₄⁻ complexes in earlier models) predominating in alkali-rich melts, and dimeric aluminum species (corresponding to Al₂Cl₇⁻ complexes in previous models) predominating in AlCl₃-rich melts. No ternary model parameters were required for the liquid phase; the binary parameters suffice. The models can be used with Gibbs free energy minimization software to calculate phase diagram sections, vapor pressures, and all thermodynamic properties at all compositions and over extended ranges of temperature and pressure.     

PVT behaviour of fluids with potential models optimised for phase equilibria

NPT and NVT Monte Carlo simulations are applied to models for methane and water to predict the PVT behaviour of these fluids over a wide range of temperatures and pressures. The potential models examined in this paper have previously been presented in the literature with their specific parameters optimised to fit phase coexistence data. The exponential-6 potential for methane gives generally good prediction of PVT behaviour over the full range of temperature and pressures studied with the only significant deviation from experimental data seen at high temperatures and pressures. The NSPCE water model shows very poor prediction of PVT behaviour, particularly at dense conditions. To improve this, the charge separation in the NSPCE model is varied with density. Improvements for vapour and liquid phase PVT predictions are achieved with this variation. No improvement was found in the prediction of the oxygen–oxygen radial distribution by varying charge separation under dense phase conditions.     

Multispectrum analysis of the ν4 band of CH3CN: Positions, intensities, self- and N2-broadening, and pressure-induced shifts

A multispectrum nonlinear least-squares fitting technique was applied to measure accurate zero-pressure line center positions, Lorentz self- and nitrogen (N₂)-broadened half-width coefficients, and self- and N₂-pressure-induced shift coefficients for over 700 transitions in the parallel ν₄ band of CH₃CN near 920 cm⁻¹. Fifteen high-resolution (0.0016 cm⁻¹) laboratory absorption spectra of pure and N₂-broadened CH₃CN recorded at room temperature using the Bruker IFS 125HR Fourier transform spectrometer located at the Pacific Northwest National Laboratory (PNNL) in Richland, Washington, USA, were analyzed simultaneously assuming standard Voigt line shapes. Short spectral intervals containing manifolds of transitions from the same value of J were fitted together. In all, high-precision line parameters were obtained for P(44)-P(3) and R(0)-R(46) manifolds. As part of the analysis, quantum assignments were extended, and the total internal partition function sum was calculated for four isotopologs: ¹²CH₃¹²CN, ¹³CH₃¹²CN, ¹²CH₃¹³CN, and ¹³CH₃¹³CN. Measurements of N₂ broadening, self-broadening, N₂-shift, and self-shift coefficients for transitions with J up to 48 and K up to 12 were measured for the first time in the mid-infrared. Self-broadened half-width coefficients were found to be very large (up to ∼2 cm⁻¹ atm⁻¹ at 296 K). Ratios of self-broadened half-width coefficients to N₂-broadened half-width coefficients show a compact distribution with rotational quantum number in both the P and R branches that range from ∼4.5 to 14 with maxima near ∣m∣=24, where m=−J″, J″, and J″+1 for P, Q, and R lines, respectively. Pressure-induced shifts for N₂ are small (few exceed ±0.006 cm⁻¹ atm⁻¹ at 294 K) and are both positive and negative. In contrast, self-shift coefficients are large (maxima of about ±0.08 cm⁻¹ atm⁻¹ at 294 K) and are both positive and negative as a function of rotational quantum numbers. The present measured half-widths and pressure shifts in ν₄ were compared with corresponding measurements of rotational transitions.     

Equilibrium of an Elastic Spherical Shell Filled with a Heavy Fluid under Pressure

This paper considers the problem of equilibrium of a nonlinearly elastic spherical shell filled with a heavy fluid and resting on a smooth, absolutely rigid, flat surface. The weight of the shell is assumed to be negligible in comparison with the weight of the fluid filling it. The contact region with the supporting plane is one of the unknowns in the problem. Equilibrium equations for a membrane shell are obtained in an accurate nonlinear formulation. Stresses and strains of a shell made of a Mooney–Rivlin material are numerically investigated. The results are compared with calculation results for the case of inflation of a spherical shell ignoring the weight of the fluid filling. The effect of the fluid weight on shell strains and stresses is estimated.     

Smoothed Particle Hydrodynamics Model of Non-Aqueous Phase Liquid Flow and Dissolution

A smoothed particle hydrodynamics model was developed to simulate the flow of mixtures of aqueous and non-aqueous phase liquids in porous media and the dissolution of the non-aqueous phase in the aqueous phase. The model was used to study the effects of pore-scale heterogeneity and anisotropy on the steady state dense non-aqueous phase liquid (DNAPL) saturation when gravity driven DNAPL displaces water from initially water saturated porous media. Pore-scale anisotropy was created by using co-oriented non-overlapping elliptically shaped grains to represent the porous media. After a steady state DNAPL saturation was reached, water was injected until a new steady state DNAPL saturation was reached. The amount of trapped DNAPL was found to be greater when DNAPL is displaced in the direction of the major axes of the soil grains than when it is displaced in the direction of the minor axes of the soil grains. The amount of trapped DNAPL was also found to increase with decreasing initial saturation of the continuous DNAPL phase. For the conditions used in our simulations, the saturation of the trapped DNAPL with a smaller initial DNAPL saturation was more than 3 times larger than the amount of trapped DNAPL with a larger initial saturation. These simulations were carried out assuming that the DNAPL did not dissolve in water. Simulations including the effect of dissolution of DNAPL in the aqueous phase were also performed, and effective (macroscopic) mass transfer coefficients were determined. The U.S. Government’s right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged.     

Analysis of realistic rough surface for its globally dominant parameters using continuous wavelets

Continuous Morlet and Mexican hat wavelets are used to analyze a highly irregular rough surface replicated from real turbine blades which are roughened by deposi-tion of foreign materials. The globally dominant aspect ratio, length scale, and orientation of the roughness elements are determined. These parameters extracted from this highly irregular rough surface are important for the future studies of their effects on turbulent flows over this kind of rough surfaces encountered in Washington aerospace and power generating industries.     

Ab initio study of H and He migrations in β-phase Sc, Y, and Er hydrides

Ab initio calculations based on the density functional theory have been performed to investigate the migrations of hydrogen(H) and helium(He) atoms in β-phase scandium(Sc),yttrium(Y),and erbium(Er) hydrides with three different ratios of H to metal.The results show that the migration mechanisms of H and He atoms mainly depend on the crystal structures of hydrides,but their energy barriers are affected by the host-lattice in metal hydrides.The formation energies of octahedral-occupancy H(H oct) and tetrahedral vacancy(V tet) pairs are almost the same(about 1.2 eV).It is of interest to note that the migration barriers of H increase with increasing host-lattice atomic number.In addition,the results show that the favorable migration mechanism of He depends slightly on the V tet in the Sc hydride,but strongly on that in the Y and Er hydrides,which may account for different behaviours of initial He release from ScT2 and ErT2.     

Homogenization and Upscaling for Diffusion,Heat Conduction,and Wave Propagation in Heterogeneous Materials

We present a general homogenization method for diffusion,heat conduction,and wave propagation in a periodic heterogeneous material with piecewise constants.The method is relevant to the frequently encountered upscaling issues for heterogeneous materials.The dispersion relation for each problem is first expressed in the general form where the frequency ω (or wavenumber k) is expanded in terms of the wavenumber k (or frequency ω).A general homogenization model can be directly obtained with any given dispersion relation.Next step we study the unit cell of the heterogeneous material and derive the exact dispersion relation.The final homogenized equations include both leading order terms (effective properties) and high order contributions that represent the effect of the microscopic heterogeneity on the macroscopic behavior.That effect can be lumped into a single dimensionless heterogeneity parameter β,which is bounded between 1/12 ≤β≤ 0 and has a universal expression for all three problems.Numerical examples validate the proposed method and demonstrate a significant computational saving.     

Ion/molecule reactions,mass spectrometry and optical spectroscopy in a linear ion trap

A linear-geometry, radio-frequency, quadrupole ion trap has been developed to generate, purify, accumulate and study atomic and molecular ions in the gas phase. By employing a trap-based system, both reactant and product ions can be stored for significant time periods, which can both enhance the efficiency of gas-phase reaction processes and create an environment to observe collision products after vibrational and rotational excitations have had time to relax. Relaxation occurs via viscous cooling with a dilute buffer gas or via laser cooling. Furthermore, the setup is particularly useful for performing optical spectroscopy on the trapped ions.Atomic and molecular ovens are used to generate thermal beams of neutral species, which are then ionized by electron bombardment. The ions can be trapped, or they can be collided with neutral molecules (e.g. C₆₀) under well defined experimental conditions. The collision energies are variable over a range from nearly 0 to 200 eV. This feature makes possible studies of complex formation, charge transfer and collision-induced fragmentation as a function of kinetic energy. A wide range of masses of up to 4000 u can be stored and manipulated with this apparatus.Two mass spectrometric techniques for the analysis of trapped ionic species are presented. In one method, parametric excitation of the secular motion is used to generate mass spectra with resolutions as high as 1 part in 800 with a simple experimental setup. The second method is capable of quickly generating mass spectra over the entire range of trapped masses, but has only moderate resolution. These spectra are generated by linearly sweeping the rf-trapping voltage to zero and detecting ions as their trap depth falls below a threshold value. In the trapping volume, which is 10 cm in length and 200 μm in diameter, 10⁶ ions can be loaded and stored, corresponding to an ion density above 10⁸ cm⁻³. Such densities facilitate spectroscopy of the stored ions. Both laser-induced fluorescence and photodissociation measurements have been carried out with a cw laser system providing near-infrared, visible, and ultraviolet beams. Absolute, total cross-sections and branching ratios of the photodissociation of MgC⁺₆₀ have been measured.     

Identification,composition, thermodynamic and structural properties of a pyroaurite-like iron(II)-iron (III) hydroxy-oxalate green rust

The aerial oxidation of aqueous suspensions of ferrous hydroxide precipitated from ferrous oxalate and caustic soda can lead to an iron (II)-iron (III) hydroxy-oxalate of the pyroaurite group, a GR(C₂O₄^2-) Green Rust. As other GR compounds, it is unstable with respect to the action of oxygen and oxidises later on. Its chemical composition was determined to be [Fe^II₆ Fe^III₂(OH)₁₆]²⁺[C₂O₄^2- · nH₂O], with n more likely equal to 3 on the basis of structural considerations. The composition does not vary and the Fe (II) / Fe (III) ratio in the compound is measured by means of transmission Mössbauer spectroscopy at 78 K and 20 K in the range from 2.8 to 3.2 for various samples at various stages of the reaction. GR(C₂O₄^2-) is paramagnetic at both temperatures and is unambiguously distinguished from ferrous hydroxide, the initial reactant, and magnetite, the main final product, which are magnetically ordered at 20 K. The spectrum of the GR compound is composed of three quadrupole doublets, one due to the Fe(III) cations characterised by a small quadrupole splitting ΔE_Q of 0.40 mm s⁻¹, and two due to the Fe(II) cations, characterised by larger ΔE_Q values of about 2.55 and 2.85 mm s⁻¹. Finally, from the observed equilibrium conditions between ferrous hydroxide and GR(C₂O₄^2-), the standard free enthalpy of formation of GR(C₂O₄^2-) was computed to be : ΔG°_f[Fe^II₆ Fe^III₂ (OH)₁₆]²⁺[C₂O₄^2- · 3H₂O] = −5383 ± 3 kJ mol⁻¹.