By applying the hypervirial-Pad6 calculation to the model Yukawa potential with a modified screening parameter, we obtain the shell binding energies of neutral atoms which yield accurate results over the entire range of the atomic number.Recently, Dutt and Varshni [1] have obtained a simple formula for the S-state shell binding energy E,s of a neutral atom as
There is very little data on the behavior of the bulk modulus of crystals over a wide temperature range. Recently, Anderson revived interest in a fundamental constant of a solid called δ, which was first introduced by Grüneisen. This parameter is similar in many respects to the well-known Grüneisen parameter γ and was used by Anderson to explain the temperature dependence of the bulk modulus of oxide compounds. In the present paper, general expressions for δ have been derived in a simple manner correlating the thermodynamical and the interatomic potential approaches. The parameter δ has also been related to the Grüneisen parameter using the Slater and Dugdale-MacDonald equations. The relative appropriateness of different expressions for δ has been discussed. The computed values of δ for NaCl- and CsCl-type alkali halides based on the Born-Mayer and the modified Born-Mayer potential forms have been reported and are found to be consistent and in essential agreement with other determinations. These values have been used to calculate the adiabatic bulk modulus as a function of temperature for KCl and NaCl. A good agreement is found with the experimental data over most of the temperature range in the neighborhood of and above the room temperature. This general accord with the predictions of theory clearly indicates that in the temperature range where the experimental data is inadequate, it is possible to predict the temperature dependence of the bulk modulus of nonoxide compounds also, using Anderson's equation and the relationships for δ developed in the present paper.
The dielectric absorption of nitromethane, benzonitrile, and acetonitrile and their binary mixtures has been studied in the microwave region over a range of temperatures in dilute benzene solutions. The data on static and optical permittivities at 20 °C have also been obtained, from measurements at 100 kHz and from measuring the refractive index for sodium-D lines, for a few cases. These data have been used to determine the relaxation times and the thermodynamic parameters for the activated state. The results obtained have been discussed in terms of the molecular motion of the systems. A new empirical relation has been proposed to represent the relaxation behaviour of a system of two Debye-type polar components in a nonpolar solvent. The relation has been tested, along with a previously suggested relation, by comparing the calculated values with those determined experimentally.
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