Clusters in
physics
Physics is the scientific study of matter, its Elementary particle, fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge whi ...
refers to small,
polyatomic
A polyatomic ion (also known as a molecular ion) is a covalent bonded set of two or more atoms, or of a metal complex, that can be considered to behave as a single unit and that usually has a net charge that is not zero, or in special case ...
particles. Any particle made of between 3 × 10
0 and 3 × 10
7 atom
Atoms are the basic particles of the chemical elements. An atom consists of a atomic nucleus, nucleus of protons and generally neutrons, surrounded by an electromagnetically bound swarm of electrons. The chemical elements are distinguished fr ...
s is considered a cluster.
The term can also refer to the organization of protons and neutrons within an atomic nucleus, e.g. the
alpha particle
Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay but may also be produce ...
(also known as "α-cluster"
Extreme α-clustering in the 18O nucleus.
/ref>), consisting of two protons and two neutrons (as in a helium
Helium (from ) is a chemical element; it has chemical symbol, symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert gas, inert, monatomic gas and the first in the noble gas group in the periodic table. Its boiling point is ...
nucleus).
Overview
Although first reports of cluster species date back to the 1940s,solid
Solid is a state of matter where molecules are closely packed and can not slide past each other. Solids resist compression, expansion, or external forces that would alter its shape, with the degree to which they are resisted dependent upon the ...
. For example, these are the color of a body, its electrical conductivity, its ability to absorb or reflect light, and magnetic phenomena such as ferromagnetism
Ferromagnetism is a property of certain materials (such as iron) that results in a significant, observable magnetic permeability, and in many cases, a significant magnetic coercivity, allowing the material to form a permanent magnet. Ferromagne ...
, ferrimagnetism
A ferrimagnetic material is a material that has populations of atoms with opposing magnetic moments, as in antiferromagnetism, but these moments are unequal in magnitude, so a spontaneous magnetization remains. This can for example occur wh ...
, or antiferromagnetism
In materials that exhibit antiferromagnetism, the magnetic moments of atoms or molecules, usually related to the spins of electrons, align in a regular pattern with neighboring spins (on different sublattices) pointing in opposite directions. ...
. These are typical collective phenomena which only develop in an aggregate of a large number of atoms.
It was found that collective phenomena break down for very small cluster sizes. It turned out, for example, that small clusters of a ferromagnetic
Ferromagnetism is a property of certain materials (such as iron) that results in a significant, observable magnetic permeability, and in many cases, a significant magnetic coercivity, allowing the material to form a permanent magnet. Ferromagne ...
material are super-paramagnetic rather than ferromagnetic. Paramagnetism
Paramagnetism is a form of magnetism whereby some materials are weakly attracted by an externally applied magnetic field, and form internal, induced magnetic fields in the direction of the applied magnetic field. In contrast with this behavior, ...
is not a collective phenomenon, which means that the ferromagnetism of the macrostate was not conserved by going into the nanostate. The question then was asked for example, "How many atoms do we need in order to obtain the collective metallic or magnetic properties of a solid?" Soon after the first cluster sources had been developed in 1980, an ever larger community of cluster scientists was involved in such studies.
This development led to the discovery of fullerenes
A fullerene is an allotrope of carbon whose molecules consist of carbon atoms connected by single and double bonds so as to form a closed or partially closed mesh, with fused rings of five to six atoms. The molecules may have hollow sphere- ...
in 1986 and carbon nanotubes
A carbon nanotube (CNT) is a tube made of carbon with a diameter in the nanometre range (nanoscale). They are one of the allotropes of carbon. Two broad classes of carbon nanotubes are recognized:
* ''Single-walled carbon nanotubes'' (''SWC ...
a few years later.
In science, a lot is known about properties of the gas
Gas is a state of matter that has neither a fixed volume nor a fixed shape and is a compressible fluid. A ''pure gas'' is made up of individual atoms (e.g. a noble gas like neon) or molecules of either a single type of atom ( elements such as ...
phase; however, comparatively little is known about the condense
Condensation is the change of the state of matter from the gas phase into the liquid phase, and is the reverse of vaporization. The word most often refers to the water cycle. It can also be defined as the change in the state of water vapor ...
d phases (the liquid
Liquid is a state of matter with a definite volume but no fixed shape. Liquids adapt to the shape of their container and are nearly incompressible, maintaining their volume even under pressure. The density of a liquid is usually close to th ...
phase and solid
Solid is a state of matter where molecules are closely packed and can not slide past each other. Solids resist compression, expansion, or external forces that would alter its shape, with the degree to which they are resisted dependent upon the ...
phase). The study of clusters attempts to bridge this gap of knowledge by clustering atoms
Atoms are the basic particles of the chemical elements. An atom consists of a nucleus of protons and generally neutrons, surrounded by an electromagnetically bound swarm of electrons. The chemical elements are distinguished from each other ...
together and studying their characteristics. If enough atoms were clustered together, eventually one would obtain a liquid or solid.
The study of atomic and molecular clusters also benefits the developing field of nanotechnology
Nanotechnology is the manipulation of matter with at least one dimension sized from 1 to 100 nanometers (nm). At this scale, commonly known as the nanoscale, surface area and quantum mechanical effects become important in describing propertie ...
. If new materials are to be made out of nanoscale particles, such as nanocatalysts and quantum computers
A quantum computer is a computer that exploits quantum mechanical phenomena. On small scales, physical matter exhibits properties of both particles and waves, and quantum computing takes advantage of this behavior using specialized hardware. C ...
, the properties of the nanoscale particles (the clusters) would first need to be understood.
See also
* Cluster chemistry
Nanoclusters are atomically precise, crystalline materials most often existing on the 0-2 nanometer scale. They are often considered kinetically stable intermediates that form during the synthesis of comparatively larger materials such as semic ...
* Nanoparticle
A nanoparticle or ultrafine particle is a particle of matter 1 to 100 nanometres (nm) in diameter. The term is sometimes used for larger particles, up to 500 nm, or fibers and tubes that are less than 100 nm in only two directions. At ...
* Nanocluster
Nanoclusters are atomically precise, crystalline materials most often existing on the 0-2 nanometer scale. They are often considered kinetically stable intermediates that form during the synthesis of comparatively larger materials such as semic ...
References
External links
Scientific community portal
for clusters, fullerenes, nanotubes, nanostructures, and similar small systems.
Nanomaterials
{{nano-tech-stub