Structural transitions and global minima of sodium chloride clusters

Abstract

In recent experiments on sodium chloride clusters structural transitions between nanocrystals with different cuboidal shapes were detected. Here we determine reaction pathways between the low energy isomers of one of these clusters, (NaCl)35Cl − . The key process in these structural transitions is a highly cooperative rearrangement in which two parts of the nanocrystal slip past one another on a {110} plane in a 110 direction. In this way the nanocrystals can plastically deform, in contrast to the brittle behaviour of bulk sodium chloride crystals at the same temperatures; the nanocrystals have mechanical properties which are a unique feature of their finite size. We also report and compare the global potential energy minima for (NaCl) N Cl − using two empirical potentials, and comment on the effect of polarization. 61.46.+w,36.40.Sx,82.30.Qt

The dynamics of structural transitions in sodium chloride clusters

“…19 Most of the global minima were the same for both potentials. 17 Given some of the other approximations we use in this study, the small advantages gained by using the Welch potential do not warrant the considerable additional computational expense. We should also note that a well-known problem associated with the above family of potentials for the alkali halides is that they never predict the CsCl structure to be the most stable.…”

“…17 This sampling was performed by repeatedly stepping across the PES from minimum to minimum via transition states, thus giving a connected set of stationary points. We biased this search to probe the lowenergy regions of the PES either by using a Metropolis criterion 21 to decide whether to accept a step to a new minimum [22][23][24] or by systematically performing transition state searches from the lower energy minima in the sample.…”

“…16 In a previous paper we identified the mechanisms of these structural transitions by extensively searching the low-energy regions of the PES of one of these clusters, (NaCl) 35 Cl − , in order to obtain paths linking the different cuboidal morphologies. 17 The key process in these transitions is a highly cooperative rearrangement in which two parts of the nanocrystal slip past one another on a {110} plane in a 110 direction.…”

Dimensional Strategies and the Minimization Problem: Barrier-Avoiding Algorithms

“…The procedure is simple to implement and has proved effective in a variety of applications. 7,9,15,16,28 The present work explores another class of minimization strategies. Broadly speaking, the approach is a potential modification technique that combines elements of both basinhopping and dimensional-relaxation strategies.…”

Characterizing the network topology of the energy landscapes of atomic clusters

“…1 The properties of these types of networks have effectively been studied before, albeit in a directed form where the links have been weighted by the rate of transition from one minimum to another at a particular temperature. [37][38][39][40] This approach leads to a rate matrix from which an exact solution of the interminimum dynamics of the system can be obtained in terms of the eigenvalues and eigenvectors of this matrix using a master equation method. However, in all these applications the emphasis was on the resulting dynamics and not on the topological structure of the networks.…”