Taming the rugged landscape: Techniques for the production, reordering, and stabilization of selected cluster inherent structures

Abstract

We report our studies of the potential energy surface ͑PES͒ of selected binary Lennard-Jones clusters. The effect of adding selected impurity atoms to a homogeneous cluster is explored. Inherent structures and transition states are found by combination of conjugate gradient and eigenvector-following methods while the topography of the PES is mapped with the help of a disconnectivity analysis. We show that we can controllably induce new structures as well as reorder and stabilize existing structures that are characteristic of higher-lying minima.

Taming the rugged landscape: Production, reordering, and stabilization of selected cluster inherent structures in the X13−nYn system

“…Both current and previous work 11 indicate that such controllable modifications are possible in model Lennard-Jones systems. In particular, we have demonstrated that by introducing impurity atoms of varying size and interaction energies, we can produce core-atom conformers that correspond to a variety of nonminimum energy homogeneous isomers.…”

“…Our hope is that such new structures might have interesting physical properties ͑electronic, magnetic, optical, thermal, etc.͒ and can be used as precursors in subsequent assembly procedures. Our previous work 11 has demonstrated that for small Lennard-Jones systems we could, using selected impurities, both alter the energy ordering of the stable core atom isomers and induce wholly new conformers not seen in the original homogeneous species. We have also seen similar reordering effects in our studies of molecular nitrogen adsorbates on nickel clusters.…”

“…Sustained progress in this emerging field of cluster assembled materials ultimately rests on the ability to characterize and control a broad range of increasingly complex nanoscale objects. In a previous paper, 11 we have examined a number of theoretical issues of general concern with respect to predicting/characterizing/controlling the structure and dynamics of cluster-based precursors. That work, in essence, seeks to invert the logic of the minimization problem.…”

“…Second, we wish to demonstrate the resulting species can be made sufficiently robust that they are of practical interest. To attain the second goal we enhance our previous publication 11 by determining Rice-Ramsperger-KasselMarcus ͑RRKM͒ isomerization rate constants and lifetimes for the generated isomers.…”

Searching for transition paths in multidimensional space with a fixed repulsive bias potential

“…The EF method has successfully been used in many cases, e.g., in studies of 2D cluster diffusion, 1 the conformations of biological molecules, 14 and the structures of binary clusters. 15 The fundamental problem in searching for saddle points in many-particle systems is that there is simply no single method that can guarantee that all saddle points have been found. In complicated systems it is thus a useful and practical strategy to try several different methods to make sure that at least the most important transition paths have been identified.…”