Volume 29, Issue 4, July 2000
Index of content:
An International Standard Formulation for the Thermodynamic Properties of 1,1,1-Trifluoroethane (HFC-143a) for Temperatures From 161 to 450 K and Pressures to 50 MPa29(2000); http://dx.doi.org/10.1063/1.1318909View Description Hide Description
A new formulation is presented for the thermodynamic properties of refrigerant 143a (1,1,1-trifluoroethane, ) based upon available experimental data. The formulation can be used for the calculation of density, heat capacity,speed of sound, energy, and saturation properties using an equation of state explicit in Helmholtz energy. Ancillary equations are given for the ideal gas heat capacity, the vapor pressure, and for the saturated liquid and vapor densities as functions of temperature. Comparisons to available experimental data are given that establish the accuracy of calculated properties using this equation of state. The estimated uncertainties of properties calculated using the new equation are 0.1% in density, 0.5% in heat capacities, 0.02% in the speed of sound for the vapor at pressures less than 1 MPa, 0.5% in the speed of sound elsewhere, and 0.1% in vapor pressure, except in the critical region. The equation is valid for temperatures from the triple point temperature (161.34 K) to 450 K and pressures up to 50 MPa, and can be extrapolated to 650 K. It has been accepted as an international standard formulation for the properties of R-143a by the International Energy Agency-Annex 18. © 2001 by the U.S. Secretary of Commerce on behalf of the United States. All rights reserved.
29(2000); http://dx.doi.org/10.1063/1.1318910View Description Hide Description
Low-energy electron collision data for the plasma processing gas are sparse. Limited cross section data are available only for total and differential elastic electron scattering, electron-impact ionization, and electron attachment. These data are assessed, synthesized, and discussed in this paper. There is a need for confirming measurements for some of these data, and for measurements of cross sections for the other main electron–collision processes for which no data exist. There are presently no data available for the electron transport,ionization, and attachment coefficients of this molecule. © 2001 by the U.S. Secretary of Commerce on behalf of the United States. All rights reserved.
29(2000); http://dx.doi.org/10.1063/1.1308292View Description Hide Description
More than 200 Madelung constants (MCs), site potentials, and electric field gradient components for ionic crystals of different nature calculated by means of the modified Madelung–Born method are presented. The same technique has helped in finding superposition rules interconnecting different classic crystals, which are useful for checking the accuracy of calculated MCs, the local site potentials, and electric field gradient tensors. The definition of Madelung interaction potentials (MIPs) is introduced, and these purely geometric quantities, independent of particular charge distribution, are found the most suitable for tabulation of crystal electric field parameters. MIPs are calculated between a number of characteristic points of fcc, bcc, hcp, and some other cells. MIPs depend strongly on the choice of cell geometric parameters but allow easy calculation of the local potentials for arbitrary point charge distribution, which are independent of this choice. The site potentials determined for yttriumceramics, fullerides, and superfullerides make it possible to examine some regularities useful for interpretation of the observed phenomena already at the electrostatic level. The comparison of the most recent results with the calculations of MC of known crystals by means of the Evald and other techniques reveals complete agreement. The advantages of the present approach are manifested in calculations of the surfaceelectrostatic parameters, which are found for a number of crystal planes, surfaces, and sets of layers including those composed of different crystals and those containing charged crystal planes. This technique can be applied for computation of MCs, site potentials, and electric field gradients for a crystal body restricted by two parallel planes, oriented arbitrarily to the crystal axes, in a layer situated at any depth from the surface.
Detailed Tabulation of Atomic Form Factors, Photoelectric Absorption and Scattering Cross Section, and Mass Attenuation Coefficients in the Vicinity of Absorption Edges in the Soft X-Ray (Z=30–36, Z=60–89, E=0.1 keV–10 keV), Addressing Convergence Issues of Earlier Work29(2000); http://dx.doi.org/10.1063/1.1321055View Description Hide Description
Reliable knowledge of the complex x-rayform factor [ and ] and the photoelectric attenuation coefficient is required for crystallography, medical diagnosis, radiation safety, and XAFS studies. Discrepancies between currently used theoretical approaches of 200% exist for numerous elements from 1 to 3 keV x-ray energies. The key discrepancies are due to the smoothing of edge structure, the use of nonrelativistic wave functions, and the lack of appropriate convergence of wave functions. This paper addresses these key discrepancies and derives new theoretical results of substantially higher accuracy in near-edge soft x-ray regions. The high-energy limitations of the current approach are also illustrated. The energy range covered is 0.1 to 10 keV. The associated figures and tabulation demonstrate the current comparison with alternate theory and with available experimental data. In general, experimental data are not sufficiently accurate to establish the errors and inadequacies of theory at this level. However, the best experimental data and the observed experimental structure as a function of energy are strong indicators of the validity of the current approach. New developments in experimental measurement hold great promise in making critical comparisons with theory in the near future.