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| Space Lattice and Unit Cell |
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| The constituent particles of a crystalline solid are arranged in a definite fashion in the three dimensional space. |
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| One such arrangement by representing the particles with points is shown below: |
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| fig 2.1 |
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| Such a regular arrangement of the constituent particles of a crystal in a three dimensional space is called crystal lattice or space lattice. |
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| From the complete space lattice, it is possible to select a smallest three dimensional portion which repeats itself in different directions to generate the complete space lattice. This is called a Unit Cell. |
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| Unit cell |
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| The smallest three-dimensional portion of a complete space lattice, which when repeated over and again in different directions produces the complete space lattice. |
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| The size and shape of a unit cell is determined by the lengths of the edges of the unit cell (a, b and c) and by the angles a, b and g between the edges b and c, c and a, and a and b respectively. |
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| If we take into consideration, the symmetry of the axial distances (a, b, c) and also the axial angles between the edges (a, b and g), the various crystals can be divided into seven systems. These are also called crystal habits. |
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