# T1 - CRYSTALLATTICE What is crystal(space lattice In...

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Crystal Structure 1 CRYSTAL LATTICE What is crystal (space) lattice? In crystallography, only the geometrical properties of the crystal are of interest, therefore one replaces each atom by a geometrical point located at the equilibrium position of that atom. Platinum Platinum surface Crystal lattice and structure of Platinum (scanning tunneling microscope)

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Crystal Structure 2 An infinite array of points in space, Each point has identical surroundings to all others. Arrays are arranged exactly in a periodic manner. Crystal Lattice α a b C B E D O A y x
Crystal Structure 3 Crystal Structure Crystal structure can be obtained by attaching atoms, groups of atoms or molecules which are called basis (motif) to the lattice sides of the lattice point. Crystal Structure = Crystal Lattice + Basis

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A two-dimensional Bravais lattice with  different choices for the basis
Crystal Structure 5 E H O A C B F b G D x y a α a b C B E D O A y x b) Crystal lattice obtained by identifying all the atoms in (a) a) Situation of atoms at the corners of regular hexagons Basis A group of atoms which describe crystal structure A group of atoms which describe crystal structure

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Crystal Structure 6 Crystal structure Don't mix up atoms with lattice points Lattice points are infinitesimal points in space Lattice points do not necessarily lie at the centre of atoms Crystal Structure = Crystal Lattice + Basis
Crystal Structure 7 Crystal Lattice Bravais Lattice (BL) Non-Bravais Lattice (non-BL) All atoms are of the same kind All lattice points are equivalent Atoms can be of different kind Some lattice points are not equivalent A combination of two or more BL

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Crystal Structure 8 Types Of Crystal Lattices 1) Bravais lattice is an infinite array of discrete points with an arrangement and orientation that appears exactly the same, from whichever of the points the array is viewed. Lattice is invariant under a translation. Nb film
Crystal Structure 9 Types Of Crystal Lattices The red side has a neighbour to its immediate left, the blue one instead has a neighbour to its right.

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T1 - CRYSTALLATTICE What is crystal(space lattice In...

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