Hexagonal Close Packed Structure The hexagonal structure is shown in fig. The hcp structure is very common for elemental metals, including: In a hexagonal close-packed (hcp) arrangement of atoms, the unit cell consists of three layers of atoms. The Miller Indices are sets of 3 numbers, labeled h, k, and l, that denote a plane (hkl) in a crystal lattice. Some metals with hexagonal close-packed crystal structures include cobalt, cadmium, zinc, and the α phase of titanium. Close-packed crystal structure characterized by the regular alternation of two layers; the atoms in each layer lie at the vertices of a series of equilateral triangles, and the atoms in one layer lie directly above the centers of the triangles in neighboring layers. In this representation a hexagon on the top and on the bottom sandwich a triangle in between the two hexagons. The second possibility is to place the atoms of the third layer over those of neither of the first two but instead over the set of holes in the first layer that remains unoccupied.… Hexagonal close-packing corresponds to a ABAB stacking of such planes. Hexagonal close packed (hcp) refers to layers of spheres packed so that spheres in alternating layers overlie one another. The top and bottom layers (a) contain six atoms at the corners of a hexagon and one atom at the center of each hexagon.The middle layer (b) contains three atoms nestled between the atoms of the top and bottom layers, hence, the name close-packed. Hexagonal close packed metals and alloys exhibit preferred orientations following thermo-mechanical treatments which result in anisotropic physical, magnetic and mechanical properties. [Def.] The numbers are the smallest integers which are reciprocals of the intercepts of the plane on the a, b, and c axes of the crystal.

The face-centered cubic (fcc) has a coordination number of 12 and contains 4 atoms per unit cell. Other articles where Hexagonal close-packed structure is discussed: crystal: Structures of metals: , which is called the hexagonal- closest-packed (hcp) structure. The body-centered cubic (bcc) has a coordination number of … Hexagonal close-packed The closest packing of spheres in two dimensions has hexagonal symmetry where every sphere has six nearest neighbors.

Hexagonal close packing of metal atoms is displayed interactively in 3D. Octahedral and tetrahedral holes are highlighted with ABA layer packing. Taking a collection of 13 such spheres gives the cluster illustrated above. …crystal with hexagonal symmetry (called hexagonal close-packed, or hcp); the other would lead to a crystal with cubic symmetry that could also be visualized as an assembly of cubes with atoms at the corners and at the centre of each face (known as face-centred cubic, or fcc). lc.