Chemical Forces: Nanoparticles

Atoms can aggregate or cluster in simple arrangements without forming a unit cell. Silica tetrahedral (SiO₃) and other tetrahedral clusters, double tetrahedral containing five atoms, pyramids containing five atoms, as well as octahedral or double pyramids containing six atoms are among the more fundamental clusters. Eight atoms form a simple cubic unit cell, while nine characterize a body-centered cubic cell, becoming more complex with face-centered cubic unit cells which can be rendered as icosahedrons of 12 atoms or 13 atoms with a body-centered or cluster-centered atom. These form building blocks for nanoparticles which can continue to add layers or shells forming layered or shell structures, even nanotubes. Many clusters and shell structures are represented by the platonic solids and their regular-face, convex polyhedra. Carbon clusters such as fullerene-based multilayer or multiconcentric clusters form unique nanoparticles. Variances of these structures form aggregates representing carbon-based soots and related nanoclusters.