Interatomic potentials for alkali metals. A comparative study

Abstract

A comparative study of interatomic potentials for alkali metals is presented. Both, the interaction functions which are derived from phonon-dispersion curves and Heine-Abarenkov-Shaw optimized model potentials are given. For comparison with experimental data some defect cslculations are made to obtain the vacancy formation and migration energies in Li, Na, K, and Rb.Eine vergleichende Untersuchung von Zwischenatompotentialen fiir Alkalimetalle wird durchgefiihrt. Beide Wecheelwirkungsfunktionen, abgeleitet aus den Phonon-Dispersionskumen und aus dem optimierten Heine-Abarenkov-Shew-Modellpotential, werden angegeben. Zum Vergleich mit experimentellen Daten werden einige Defektberechnungen durchgefiihrt, um die Leerstellenbildungs-und die Leerstellenwanderungsenergie in Li, Na, K-und Rb zu erhelten. Computational Method Empirical p o t e n t i d sThe empirical potential functions for Li, Na, K, and Rb were constructed following the unrelaxed vacancy formation energy (EV"); an approximation of the potential function at r, = 0.6r1 (rl first-nearest-neighbour the procedure as described in Section 3 of [Z, 31 using the following input date: distance) ; l) Mekelweg 16,2600 GA Delft, Nederland. *) Nijenborgh 18,9747 AG Groningen, The Netherlands. 15 physica (b) 90/1

Temperature control algorithms in dual control volume grand canonical molecular dynamics simulations of hydrogen diffusion in palladium

“…To yield a low H:Pd ratio as the experimental results presented in Ref. 28, we set the chemical potential of type 1 hydrogen in control volume A ͑denoted as CV A t 1 ͒ to be 2.7ϫ 10 −19 J / mol and the chemical potential of type 2 in control volume A ͑CV A t 2 ͒ to be 2.6ϫ 10 −19 J / mol for temperatures between 661 and 967 K. Similarly, we set the chemical potentials of type 1 and type 2 hydrogen atoms in control volume B as CV B t 1 = 2.6ϫ 10 −19 J / mol and CV B t 2 = 2.7ϫ 10 −19 J / mol. Note that the total hydrogen ͑sum of type 1 and type 2͒ chemical potential is the same for each CV.…”

“…It is a slight modification of the nearest neighbor model developed by van Heugten and de Hosson. 28 When r Ͼ r 0 , the potential is set to zero. The parameters A s and r 0 used in our calculations are given in Table I.…”