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Crystalline structures based on packing of hard spheres




I need an introduction similar to this related to the same subject with is the crystalline structures, if you can paraphrase it in a way that does not make it plagiarized then that's fine too;2 Crystalline structures based on packing of hard spheres;2.1 Introduction;The bonding energy between pairs of atoms is minimized at a xed equilibrium distance r0, because of this;most solid materials spontaneously adopt a crystalline arrangement in which atoms or ions are positioned;along an ordered periodic array called the crystalline lattice. All metals, and most covalent and ionic;solids, form crystalline structures under normal solidication conditions. Many properties of crystalline;solids depend on the crystal structure, being the manner in which atoms or ions are spatially arranged.;When the atoms favor no particular bonding orientations, the crystalline structure can be conveniently;described using the hard sphere model. As metallic bonding is nondirectional in nature, the structure of;most elemental metals is accurately described by the dense packing of hard spheres. In this model, hard;spheres representing nearest neighboring atoms touch one another and form a densely packed structure. In;case of elemental metals, all the atoms are identical. Three relatively simple crystal structures are found for;most metals: face-centered cubic (FCC), hexagonal close-packed (HCP) and body centered cubic (BCC).;FCC and HCP correspond to very dense atomic arrangements called closed packed structure, while BCC is;a less dense structure.;Crystal structures determine most of the properties of a material. It can be witnessed in the beautiful;natural formations of minerals, or in a more indirect way in industry. For example, turbine blades for ghter;jets are grown such that only one crystal orientation is possible within the whole blade. Because of that;specic structure, the blade will not deform when exposed to extreme heat. This is only one of the many;consequences of the study of crystallography.


Paper#16201 | Written in 18-Jul-2015

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