Fullerene structure and properties, Physics

 

 

FULLERENE: The fullerene is a cage like hollow molecules composed of hexagonal and pentagonal groups of atoms, and especially those formed from carbon, that constitute the third form of carbon after diamond and graphite. However the term has been widened to contain any closed cage structure having more than twenty carbon atoms including completely of three coordinate carbon atoms. A, hollow pure carbon molecule in which the atoms positioned at the vertices of a polyhedron with 12 pentagonal faces and any number (other than one) of hexagonal faces. The fullerene is a just revealed family of carbon allotropes (any two or more forms of the same chemical element) named after the sheet from being planner.

STRUCTURE AND PROPERTIES: - In the fullerene molecule an even number of carbon atoms are arranged over the surface of a closed hollow cage. Each atom is trigonally linked to its three near neighbours by bonds that delineate a polyhedral network, consisting of 12 pentagonal and n hexagons (n may be any number other that one including zero). All 60 atoms in fullerenes 60 are equivalent and lie on the surface distributed with the symmetry of a truncated icosahedrons (an icosahedrons is a polyhedron having 20 faces, but usually a regular icosahedrons is meant, which has faces which are equilateral triangles). The 12 pentagons are isolated and spread symmetrically among 20 linked hexagons. Solid C60 exhibits interesting dynamic behaviour in that at room temperature the individual round molecules in the face centred cubic crystals are rotating isotropic ally (that is freely) at around 108Hz. At around 260k (8.3F) there is a phase transition to a simple cubic lattice accompanied by an abrupt lattice contraction rotation is no longer free, and the individual molecules make rotational jumps between two favoured (relative) orientations configurations, in the lower energy one a double bond lies over a pentagon, and in the other it lies over a hexagon. At 900k (-300 F) the individual molecules stop rotating altogether, freezing into the orientation ally discovered crystal involving a mix of the two configurations.

 

 

Posted Date: 7/9/2012 3:11:10 AM | Location : United States







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