FCC y HCP méndez

FCC AND HCP STRUCTURES ESTRUCTURAS FCC Y HCP

Introduction

Mendez, C. Chemical engineering student Abstrac

 Tras comprend comprender er el comporta comportamiento miento de los átomos y sus fuerzas moleculares, podemos hablar más acerca de la estructura de muchos materiales como por ejemplo los metales, la estructura de estos materiales adquiere una organización cristalina, otorgando características a especiales a cada uno de estos. En este corto articulo, se verán dos estructuras cristalinas formadas por algunos metales, la FCC y la HCP donde se explicaran de manera clara y breve. Summary

After understand the behave of the atoms and its molecular forces, we can talk about the structure of many materials such as for instance metals, the structure of this materials acquire a crystalline arrangement, giving special characteristics to each one. In this article will be seen two crystalline structures formed by some metals, the FCC and HCP in which will be explained clearly and easily.

Solid materials can be classified according atoms or ions are located one respect each other, something called atomic stacking sequence. That could be of short-range; non crystalline order (amorphous) or large-range order; crystalline order. Stacking sequence must preserve electrical neutrality, covalent bonds, minimize ion´s repulsions and stack atoms as packageable as possible.  The bravais bravais lattices lattices are arranged arranged net types, types, that are repeated in which it can fill the whole space, this lattices are infinite points that can generate vector, these kinds of  lattices are projections of atoms stacking sequences, crystalline models. In this document we will see these arranged atoms in two kinds of crystalline structures FCC and HCP, we will also see some similarities and difference between these structures.

APF=

Metallic crystal structures

APF= APF=

Structures formed by metals is due to the atoms, they self  organize un crystals most of the times. The unit cell is the smallest structure that repeats itself, forming symmetrical units like a crystal.  These unit cells are known as bravias lattice, in which a set of points are repeated, as a single point can be translated, as a set of vectors, the lattice can be formed.

APF=

In the 3-d structure, there are fourth teen Bravais lattices. APF= One of the most common types are the face centered cubic (FCC) and the hexagonal close-packed (HCP) The important properties in these structures are the type of  atom and its radius, the cell dimension, for each structure, the number of atoms per unit, coordination number (number of nearest neighbors and the atomic packing factor (APF), (the volume of all atoms in a unit cell divided by the volume of the unit cell) FCC

APF=0.74  This means that for FCC 74% is occupied by atoms

APF=

Metallic crystal structures

APF= APF=

Structures formed by metals is due to the atoms, they self  organize un crystals most of the times. The unit cell is the smallest structure that repeats itself, forming symmetrical units like a crystal.  These unit cells are known as bravias lattice, in which a set of points are repeated, as a single point can be translated, as a set of vectors, the lattice can be formed.

APF=

In the 3-d structure, there are fourth teen Bravais lattices. APF= One of the most common types are the face centered cubic (FCC) and the hexagonal close-packed (HCP) The important properties in these structures are the type of  atom and its radius, the cell dimension, for each structure, the number of atoms per unit, coordination number (number of nearest neighbors and the atomic packing factor (APF), (the volume of all atoms in a unit cell divided by the volume of the unit cell)

APF=0.74  This means that for FCC 74% is occupied by atoms

FCC

HCP

APF=

APF=

APF=

APF=0,74  This means that for FCC 74% is occupied by atoms The HCP and FCC are packed structures both, with an APF of 74%  but they are not identical due to the stacking arrangement of the atoms  plane. They also have a coordination number of 12 but as we mentioned they differ in the stacking sequence.

HCP

APF=

APF=

APF=

APF=0,74  This means that for FCC 74% is occupied by atoms The HCP and FCC are packed structures both, with an APF of 74%  but they are not identical due to the stacking arrangement of the atoms  plane. They also have a coordination number of 12 but as we mentioned they differ in the stacking sequence.

In the next image we will see the FCC layer and the HCP layer, the HCP layers cycle among the two equivalent shifted positions whereas the FCC layers cycle between three positions. These atoms arrange make FCC metal structures be ductile than HCP metals

Structures formed by metals are due to the atoms, the unit cell is the smallest structure that repeats itself, forming symmetrical units like a crystal. References

HCP =ABAB FCC=ABCABC http://www.ndted.org/EducationResources/CommunityCollege/Materials/Structu re/fcc_hcp.htm

Conclusions

Bravias lattices are arranged net types that are repeated in which it can fill the whole space.

In the next image we will see the FCC layer and the HCP layer, the HCP layers cycle among the two equivalent shifted positions whereas the FCC layers cycle between three positions. These atoms arrange make FCC metal structures be ductile than HCP metals

Structures formed by metals are due to the atoms, the unit cell is the smallest structure that repeats itself, forming symmetrical units like a crystal. References

HCP =ABAB FCC=ABCABC http://www.ndted.org/EducationResources/CommunityCollege/Materials/Structu re/fcc_hcp.htm

Conclusions

Bravias lattices are arranged net types that are repeated in which it can fill the whole space.