Analysis of the equation of state of lithium and sodium halides

Abstract

A theoretical analysis of the equation of state is performed for the halides of lithium and sodium. The variation of volomo with pressure is calculated using seven different potential functions for the short-range overlap repulsive energy. The van der Waals dipole-dipole and dipole-qnadrupole interactions derived from thevariational method are taken into account. The results obtained are compared with available experimental data. I n most of the crystals studied, the Varshni-Shukla exponential potential for the repulsive energy gives the best agreement with experimental data for the equation of state.Eine theoretische Analyse der Zustandsgleichung wird fur die Lithium-und Natriumhalogenide durchgefuhrt. Die Volumeniinderung unter Druck wird mit sieben unterschiedlichen Potentialfunktionen fur kurzreichweitige repulsive nerlappungsenergien berechnet. Dabei werden van der Waals-Dipol-Dipol-und -Dipol-Quadrupol-Wechselwirkungen berucksichtigt, die mit einer Variationsmethode abgeleitet werden. Die erhaltenen Ergebnisse werden mit vorhandenen experimentellen Werten verglichen. In den meisten der untersuchten Kristalle ergibt das exponentielle Varshni-Shukla-Potential die beste ubereinstimmung mit den experimentellen Daten fur die Zustandsgleichung.

Dielectric Constants and Their Pressure and Temperature Derivatives for Ionic Crystals

“…where A is the short-range interaction force constant and p the reduced mass per ion pair, and ro is the equilibrium value of nearest-neighbour interionic separation. It was shown for the first time by Szigeti that (28) and (29) were not satisfied with the available experimental data on dielectric constants, transverse optical mode frequencies oTo, and isothermal compressibility K for alkali halides and other ionic crystals. The original findings of Szigeti were subsequently confirmed by Lowndes and Martin [7l with their more accurate experimental data corresponding to room temperature as well as low temperature.…”

Analysis of the Equation of State of Ammonium Halides

“…where k = 1.54 for CsCl lattice and 2 for NaCl lattice, Equations (4), (7), and (9) yield (9) Here k, = 2 1/3/3 and 1/2 for CsCl and NaCl lattice, respectively. The input data [4, 7, 101 a t room temperature are compiled in Table 1 along with calculated values of parameters b and e.…”

Equation of State and Pressure Dependence of the Grüneisen Parameter for NaCl Crystal

“…The equation of state of a solid can be written as [7,8] [ll] are given in parentheses [20]. (b) Calculated using Dugdale and MacDonald's theory [21].…”