Degree Type

Dissertation

Date of Award

1991

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

Andrew E. DePristo

Abstract

The structure and energetics of Ni[subscript] N and Pd[subscript] N clusters (4 ≤ N ≤ 23) are investigated using a corrected effective medium (CEM) theory. Computational developments enabling this research are also discussed--including the formulation of the analytic derivative of the kinetic, exchange and correlation energy functionals within the additive density approximation of the CEM theory and its implementation onto a nCUBE 2 hypercube computer;Unique structural features of these metal clusters are noted especially in relation to the bulk and surface phases of Ni and Pd and to structures commonly associated with rare gas clusters. For many cluster sizes stable structures of the transition metal clusters differ substantially from those of rare gas clusters. These differences are rationalized in terms of the differences in the nature of the atomic interactions in the two types of systems. Generally, the structure of the Ni[subscript] N and Pd[subscript] N clusters maximizes the minimum coordination of any atom, whereas the structure of rare gas clusters maximizes the number of interatomic distances close to the optimal distance for interaction between rare gas atoms. The latter can be interpreted as the packing of hard balls. Also, structural transformations between isomers of similar energy are examined for selected sizes;The kinetic, exchange and correlation energies are evaluated efficiently by use of a massively parallel hypercube computer. Details of the implementation and analysis of its performance in comparison with more conventional, shared memory computers is discussed. The speedup observed on the hypercube is nearly linear with increasing numbers of processing elements.

DOI

https://doi.org/10.31274/rtd-180813-12755

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Mark Shawn Stave

Language

en

Proquest ID

AAI9207255

File Format

application/pdf

File Size

167 pages

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