Complex metallic alloys (CMAs) or complex intermetallics (CIMs) are intermetallic compounds characterized by the following structural features: #large unit cells, comprising some tens up to thousands of atoms, #the presence of well-defined atom clusters, frequently of icosahedral point group

symmetry Symmetry () in everyday life refers to a sense of harmonious and beautiful proportion and balance. In mathematics, the term has a more precise definition and is usually used to refer to an object that is Invariant (mathematics), invariant und ...

, #the occurrence of inherent disorder in the ideal structure.

Overview

''Complex metallic alloys'' is an umbrella term for intermetallic compounds with a relatively large unit cell. There is no precise definition of how large the unit cell of a complex metallic alloy has to be, but the broadest definition includes Zintl phases, skutterudites, and Heusler compounds on the most simple end, and

quasicrystal A quasiperiodicity, quasiperiodic crystal, or quasicrystal, is a structure that is Order and disorder (physics), ordered but not Bravais lattice, periodic. A quasicrystalline pattern can continuously fill all available space, but it lacks trans ...

s on the more complex end.

Research

Following the invention of

X-ray crystallography X-ray crystallography is the experimental science of determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to Diffraction, diffract in specific directions. By measuring th ...

techniques in the 1910s, the atomic structure of many compounds was investigated. Most

metal A metal () is a material that, when polished or fractured, shows a lustrous appearance, and conducts electrical resistivity and conductivity, electricity and thermal conductivity, heat relatively well. These properties are all associated wit ...

s have relatively simple structures. However, in 1923

Linus Pauling Linus Carl Pauling ( ; February 28, 1901August 19, 1994) was an American chemist and peace activist. He published more than 1,200 papers and books, of which about 850 dealt with scientific topics. ''New Scientist'' called him one of the 20 gre ...

reported on the structure of the intermetallic NaCd₂, which had such a complicated structure he was unable to fully explain it. Thirty years later, he got as far as finding that NaCd₂ contained about 384 sodium and 768 cadmium atoms in each unit cell. Most physical properties of CMAs show distinct differences with respect to the behavior of normal metallic alloys and therefore these materials possess a high potential for technological application. The

European Commission The European Commission (EC) is the primary Executive (government), executive arm of the European Union (EU). It operates as a cabinet government, with a number of European Commissioner, members of the Commission (directorial system, informall ...

funded the Network of Excellence CMA from 2005 to 2010, uniting 19 core groups in 12 countries. From this emerged the European Integrated Center for the Development of New Metallic Alloys and Compounds (previously C-MAC, now ECMetAC), which connects researchers at 21 universities.

Examples

Example phases are: *β- Mg₂Al₃: 1168 atoms per unit cell, face-centred

cubic Cubic may refer to: Science and mathematics * Cube (algebra), "cubic" measurement * Cube, a three-dimensional solid object bounded by six square faces, facets or sides, with three meeting at each vertex ** Cubic crystal system, a crystal system w ...

, atoms arranged in Friauf polyhedra. *ξ'–Al₇₄Pd₂₂Mn₄: 318 atoms per unit cell, face-centred orthorhombic, atoms arranged in Mackay-type clusters. * (Bergman phase): 163 atoms per unit cell, body centred cubic, atoms arranged in Bergman clusters. * (Taylor phase): 204 atoms per unit cell, face-centred orthorhombic, atoms arranged in Mackay-type clusters.

Overview

Research

Examples

See also

References

Further reading