Allan H. Harvey

Revised Formulation for the Refractive Index of Water and Steam as a Function of Wavelength, Temperature, and Density

Schiebener et al. published a formulation for the refractive index of water and steam in 1990 [J. Phys. Chem. Ref. Data 19, 677 (1990)]. It covered the ranges 0.2 to 2.5 μm in wavelength, −12 to 500 °C in temperature, and 0 to 1045 kg m−3 in density. The formulation was adopted by the International Association for the Properties of Water and Steam (IAPWS) in 1991. In the present article, the data, after conversion to ITS-90, have been refitted to the same functional form, but based on an improved equation of state for water adopted by IAPWS in 1995. The revised coefficients are reported, and some tabular material is provided. The revised refractive-index formulation was adopted by IAPWS in 1997 and is available as part of a National Institute of Standards and Technology Standard Reference Database. For most conditions, the revised formulation does not differ significantly from the previous one. A substantial improvement has been obtained in supercooled water at ambient pressure, where the previous formula...

Henry’s Constants and Vapor–Liquid Distribution Constants for Gaseous Solutes in H2O and D2O at High Temperatures

We have developed correlations for the Henry’s constant kH and the vapor–liquid distribution constant KD for 14 solutes in H2O and seven solutes in D2O. The solutes considered are common gases that might be encountered in geochemistry or the power industry. Solubility data from the literature were critically assessed and reduced to the appropriate thermodynamic quantities, making use of corrections for nonideality in the vapor and liquid phases as best they could be computed. While the correlations presented here cover the entire range of temperatures from near the freezing point of the solvent to high temperatures approaching its critical point, the main emphasis is on representation of the high-temperature behavior, making use of asymptotic relationships that constrain the temperature dependence of kH and KD near the critical point of the solvent.

Correlation for the Second Virial Coefficient of Water

A new correlation has been developed to represent the second virial coefficient of water (H2O) as a function of temperature. The formulation was fitted to experimental data, both for the second virial coefficient itself and for a quantity related to its first temperature derivative, at temperatures between approximately 310 and 1170 K. The high-temperature extrapolation behavior was guided by results calculated from a high-quality intermolecular pair potential. The new correlation agrees well with the experimental data deemed to be reliable, and at high temperatures is a significant improvement over the best previous formulation.

Potential energy surface for interactions between two hydrogen molecules

Nonrelativistic clamped-nuclei energies of interaction between two ground-state hydrogen molecules with intramolecular distances fixed at their average value in the lowest rovibrational state have been computed. The calculations applied the supermolecular coupled-cluster method with single, double, and noniterative triple excitations [CCSD(T)] and very large orbital basis sets-up to augmented quintuple zeta size supplemented with bond functions. The same basis sets were used in symmetry-adapted perturbation theory calculations performed mainly for larger separations to provide an independent check of the supermolecular approach. The contributions beyond CCSD(T) were computed using the full configuration interaction method and basis sets up to augmented triple zeta plus midbond size. All the calculations were followed by extrapolations to complete basis set limits. For two representative points, calculations were also performed using basis sets with the cardinal number increased by one or two. For the same two points, we have also solved the Schrodinger equation directly using four-electron explicitly correlated Gaussian (ECG) functions. These additional calculations allowed us to estimate the uncertainty in the interaction energies used to fit the potential to be about 0.15 K or 0.3% at the minimum of the potential well. This accuracy is about an order of magnitude better than that achieved by earlier potentials for this system. For a near-minimum T-shaped configuration with the center-of-mass distance R=6.4 bohrs, the ECG calculations give the interaction energy of -56.91+/-0.06 K, whereas the orbital calculations in the basis set used for all the points give -56.96+/-0.16 K. The computed points were fitted by an analytic four-dimensional potential function. The uncertainties in the fit relative to the ab initio energies are almost always smaller than the estimated uncertainty in the latter energies. The global minimum of the fit is -57.12 K for the T-shaped configuration at R=6.34 bohrs. The fit was applied to compute the second virial coefficient using a path-integral Monte Carlo approach. The achieved agreement with experiment is substantially better than in any previous work.

Intermolecular potential and second virial coefficient of the water-hydrogen complex

We construct a rigid-body (five-dimensional) potential-energy surface for the water-hydrogen complex using scaled perturbation theory (SPT). An analytic fit of this surface is obtained, and, using this, two minima are found. The global minimum has C2v symmetry, with the hydrogen molecule acting as a proton donor to the oxygen atom on water. A local minimum with Cs symmetry has the hydrogen molecule acting as a proton acceptor to one of the hydrogen atoms on water, where the OH bond and H2 are in a T-shaped configuration. The SPT global minimum is bound by 1097 microEh (Eh approximately 4.359744 x 10(-18) J). Our best estimate of the binding energy, from a complete basis set extrapolation of coupled-cluster calculations, is 1076.1 microEh. The fitted surface is used to calculate the second cross virial coefficient over a wide temperature range (100-3000 K). Three complementary methods are used to quantify quantum statistical mechanical effects that become significant at low temperatures. We compare our results with experimental data, which are available over a smaller temperature range (230-700 K). Generally good agreement is found, but the experimental data are subject to larger uncertainties.

Reference Correlations for Thermophysical Properties of Liquid Water at 0.1MPa

Simple but highly accurate correlations have been developed for the thermodynamic properties (including density, heat capacity, and speed of sound), viscosity, thermal conductivity, and static dielectric constant of liquid water as a function of temperature at a pressure of 0.1MPa. The calculations may be simply extended to a pressure range from the saturation pressure to 0.3MPa. The temperature range covered in most cases is from 253.15to383.15K; this includes some temperatures where liquid water is metastable. These correlations are designed to reproduce the best available data, which in most cases are described by formulations issued by the International Association for the Properties of Water and Steam (IAPWS). The equations presented here are simple enough to be used in applications such as spreadsheets. They provide a convenient alternative to the more complicated IAPWS formulations in cases where only liquid properties at near-atmospheric pressure are of interest without increasing the uncertainty ...

Intermolecular potentials and second virial coefficients of the water–neon and water–argon complexes

We construct potential-energy surfaces for the water–neon and water–argon complexes from scaled perturbation theory, and calibrate them using accurate supermolecule data. Our best estimates of the binding energies for these two systems are 66.9 and 142.7 cm−1, respectively, where the latter value is in good agreement with the spectroscopically determined AW2 potential. We calculate second virial coefficients, B12(T), and the related property φ12=B12−T(dB12/dT), and compare our results with experimental data for water–argon. The perturbation theory and AW2 B12(T) results are consistent, and demonstrate that current theoretical approaches yield more precise second virial coefficient data than any in the literature. Our φ12 calculations are in good agreement with experimental results derived from enthalpy-of-mixing data, though our estimated uncertainties are significantly smaller.

New Equations for the Sublimation Pressure and Melting Pressure of H2O Ice Ih

New reference equations, adopted by the International Association for the Properties of Water and Steam (IAPWS), are presented for the sublimation pressure and melting pressure of ice Ih as a function of temperature. These equations are based on input values derived from the phase-equilibrium condition between the IAPWS-95 scientific standard for thermodynamic properties of fluid H2O and the equation of state of H2O ice Ih adopted by IAPWS in 2006, making them thermodynamically consistent with the bulk-phase properties. Compared to the previous IAPWS formulations, which were empirical fits to experimental data, the new equations have significantly less uncertainty. The sublimation-pressure equation covers the temperature range from 50 K to the vapor–liquid–solid triple point at 273.16 K. The ice Ih melting-pressure equation describes the entire melting curve from 273.16 K to the ice Ih–ice III–liquid triple point at 251.165 K. For completeness, we also give the IAPWS melting-pressure equation for ice III,...

First-Principles Calculation of the Third Virial Coefficient of Helium

Knowledge of the pair and three-body potential-energy surfaces of helium is now sufficient to allow calculation of the third density virial coefficient, C(T), with significantly smaller uncertainty than that of existing experimental data. In this work, we employ the best available pair and three-body potentials for helium and calculate C(T) with path-integral Monte Carlo (PIMC) calculations supplemented by semiclassical calculations. The values of C(T) presented extend from 24.5561 K to 10 000 K. In the important metrological range of temperatures near 273.16 K, our uncertainties are smaller than the best experimental results by approximately an order of magnitude, and the reduction in uncertainty at other temperatures is at least as great. For convenience in calculation of C(T) and its derivatives, a simple correlating equation is presented.

Physical Properties of Water

Publisher Summary Water is probably the most familiar chemical compound in human experience, and also the most necessary one. Sciences as diverse as biochemistry, meteorology, and geology require knowledge of the properties of water and aqueous solutions. In industry, water is an important part of many processes, and understanding of its properties is often necessary for design and optimization, particularly in fluids-based industries, such as chemical processing. A water molecule has a dipole moment and dipole polarizability. The key feature of the waters microscopic structure is hydrogen bonding. Because of the geometry and charge distribution of the water molecule, it tends to favor tetrahedral coordination with its neighbors. At higher temperatures, the thermal energy produces random configurations, so the amount of hydrogen bonding decreases with temperature. Because certain natural processes produce a slight fractionation between water molecules containing different isotopes, scientists can use isotopic compositions to trace processes such as global atmospheric circulation. Most people are at least qualitatively familiar with the transitions of water among vapor, liquid, and solid phases. It is customary and useful to represent this information with a phase diagram. The chapter reviews the thermodynamic, transporting, and other miscellaneous properties of water.