Complex metallic

alloys An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductility, ...

(CMAs) or complex intermetallics (CIMs) are

intermetallic An intermetallic (also called an intermetallic compound, intermetallic alloy, ordered intermetallic alloy, and a long-range-ordered alloy) is a type of metallic alloy that forms an ordered solid-state compound between two or more metallic eleme ...

compounds characterized by the following structural features: #large

unit cell In geometry, biology, mineralogy and solid state physics, a unit cell is a repeating unit formed by the vectors spanning the points of a lattice. Despite its suggestive name, the unit cell (unlike a unit vector, for example) does not necessaril ...

s, comprising some tens up to thousands of atoms, #the presence of well-defined atom clusters, frequently of

icosahedral In geometry, an icosahedron ( or ) is a polyhedron with 20 faces. The name comes and . The plural can be either "icosahedra" () or "icosahedrons". There are infinitely many non- similar shapes of icosahedra, some of them being more symmetrica ...

point group In geometry, a point group is a mathematical group of symmetry operations (isometries in a Euclidean space) that have a fixed point in common. The coordinate origin of the Euclidean space is conventionally taken to be a fixed point, and every p ...

symmetry Symmetry (from grc, συμμετρία "agreement in dimensions, due proportion, arrangement") in everyday language refers to a sense of harmonious and beautiful proportion and balance. In mathematics, "symmetry" has a more precise definit ...

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

Overview

''Complex metallic alloys'' is an umbrella term for

compounds with a relatively large

. 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 phase In chemistry, a Zintl phase is a product of a reaction between a group 1 (alkali metal) or group 2 ( alkaline earth metal) and main group metal or metalloid (from groups 13, 14, 15, or 16). It is characterized by intermediate metallic/ ionic bond ...

skutterudite Named after Skuterudåsen, a hill in Modum, Norway, skutterudite is a cobalt arsenide mineral containing variable amounts of nickel and iron substituting for cobalt with the ideal formula CoAs3. Some references give the arsenic a variable formula ...

s, and

Heusler compound Heusler compounds are magnetic intermetallics with face-centered cubic crystal structure and a composition of XYZ (half-Heuslers) or X2YZ (full-Heuslers), where X and Y are transition metals and Z is in the p-block. The term derives from the name ...

s on the most simple end, and

quasicrystal A quasiperiodic crystal, or quasicrystal, is a structure that is ordered but not periodic. A quasicrystalline pattern can continuously fill all available space, but it lacks translational symmetry. While crystals, according to the classical cr ...

s on the more complex end.

Research

Following the invention of

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

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

metal A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...

s have relatively simple structures. However, in 1923

Linus Pauling Linus Carl Pauling (; February 28, 1901August 19, 1994) was an American chemist, biochemist, chemical engineer, peace activist, author, and educator. He published more than 1,200 papers and books, of which about 850 dealt with scientific top ...

reported on the structure of the

NaCd₂, which had such a complicated structure he was unable to fully explain it. Thirty years later, he concluded that NaCd₂ contains 384 sodium and 768 cadmium atoms in each

. 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 executive of the European Union (EU). It operates as a cabinet government, with 27 members of the Commission (informally known as "Commissioners") headed by a President. It includes an administrative body o ...

funded the Network of Excellence CM

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 C-MA

which connects researchers at 21 universities.

Examples

Example phase (matter), phases are: *β- Mg₂Al₃: 1168 atoms per unit cell, face-centred cubic, atoms arranged in Friauf polyhedra. *ξ'–Al₇₄Pd₂₂Mn₄: 318 atoms per unit cell, face-centred

orthorhombic In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a r ...

, atoms arranged in Mackay-type clusters. * Mg₃₂(Al,Zn)₄₉ (Bergman phase): 163 atoms per unit cell, body centred cubic, atoms arranged in Bergman clusters. *Al₃Mn (Taylor phase): 204 atoms per unit cell, face-centred orthorhombic, atoms arranged in Mackay-type clusters.

Overview

Research

Examples

See also

References

Further reading