FCC STRUCTURE
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The document discusses properties of a face centered cubic (FCC) crystal structure. An FCC crystal has: 1) A unit cell with 4 atoms located at the corners and face centers of the cube. 2) An atomic radius of a/√22 where a is the lattice parameter. 3) A nearest neighbor distance of a/2 between adjacent atoms. 4) A coordination number of 12, atomic packing fraction of 0.74, and void space of 26%.
FCC STRUCTURE
- 1. Properties of FCC CRYSTAL
- 2. The constituent particles of a crystalline solid are arranged in a definite fashion in the three dimensional space. Such a regular arrangement of the constituent particles of a crystal in a three dimensional space is called crystal lattice or space lattice. Crystal Structure
- 3. TYPES OF CUBIC CRYSTAL
- 4. UNIT CELL CHARACTERISTICS Volume of Unit Cell No of atoms per unit cell Atomic radius Nearest neighbour distance Coordination number Atomic Packing Fraction Void space Density
- 5. 1) Volume of the unit cell : V= a3 FACE CENTRED CUBIC (FCC) CELL
- 6. 2) Effective Number of Atoms per unit Cell (Z): Z = 4 3) Atomic Radius (r) : In face centered unit cubic cell, atoms situated at the corners are not in contact with each other. They are in contact with the atom situated at the face centered atom of the cell. r = a/ 22 FACE CENTRED CUBIC (FCC) CELL
- 7. 4) Nearest Neighbor Distance, 2r : The centre to centre distance between any two adjacent neighbor atoms is called ‘Nearest Neighbor Distance’. In case of Face Centered Cubic Unit Cell, NND = a/ 2 5) Coordination Number, CN : CN= 12 FACE CENTRED CUBIC (FCC) CELL
- 8. 6) Atomic Packing Fraction (APF): The fraction of actual volume of the unit cell occupied by the atoms is called ‘atomic packing fraction’. FACE CENTRED CUBIC (FCC) CELL
- 9. 7) Void Space= (1-APF)X100% Void Space = 26 % 8) Volume mass Density ( r ): The ratio of mass to volume is called volume mass density of the cell. Therefore it is given by- W=M/NA Z (W) V Z (M/NA) a3 4M NA a3 r = r = r = FACE CENTRED CUBIC (FCC) CELL