Structure shape and stability of nanometric sized particles

Nanoparticles are a state of matter that has properties different from eith er molecules or bulk solids. In the present work, we review the shape and s tructure of nanometer-sized particles; several shapes are discussed, such a s the octahedron and truncated octahedron, the icosahedron, the Marks decah edron, the truncated "star-like" decahedron, the rounded decahedron and the regular decahedron. Experimental high-resolution transmission electron mic roscopy (TEM) images of each type of particle are presented together with t he Fast Fourier Transform and a model of the particle. We consider only gol d particles grown by vapor deposition or by colloidal methods. High-resolut ion TEM images of the particles in different orientations are shown. We dis cuss two basic types of particles uncapped and capped. Data for other metal s and semiconductors are reviewed. We have also performed very extensive si mulations obtaining the total energy and pair correlation functions for eac h cluster under study. Furthermore, distributions of single atom energy for every cluster are displayed in order to reveal the effect of surface on th e stability of different types and sizes of clusters. We discuss the struct ure of the particles from similar to1 to similar to 100 nm. The mechanisms for stress release as the particles grow larger are reviewed and a mechanis m is suggested. Finally, we discuss the parameters that define the shape of a nanoparticle and the possible implications in technological applications . (C) 2001 American Vacuum Society.