The regular three dimensional arrangement of points in a crystal is known as crystal lattice and the smallest repeating pattern in the lattice is called unit cell. The unit cells are characterised by the edge lengths a, b, c and the angles between them `alpha, beta and gamma` respectively. Based on this, there are seven crystal systems. In a cubic unit cell: `a=b=c and alpha = beta=gamma=90^(@)` The number of points in simple, body centred and face centred cubic cells are 1,2 and 4 respectively In both the hcp and ccp of spheres, the number of tetrahedral voids per sphere is two while the octahedral voids is one. A double triangular void surrounded by three spheres above and three spheres below is calledA. triangular voidB. tetrahedral voidC. octahedral voidD. trigonal bipyramidal void.

The regular three dimensional arrangement of points in a crystal is kn

1.	The regular three dimensional arrangement of points in a crystal is known as crystal lattice and the smallest repeating pattern in the lattice is called unit cell. The unit cells are characterised by the edge lengths a, b, c and the angles between them `alpha, beta and gamma` respectively. Based on this, there are seven crystal systems. In a cubic unit cell: `a=b=c and alpha = beta=gamma=90^(@)` The number of points in simple, body centred and face centred cubic cells are 1,2 and 4 respectively In both the hcp and ccp of spheres, the number of tetrahedral voids per sphere is two while the octahedral voids is one. A double triangular void surrounded by three spheres above and three spheres below is calledA. triangular voidB. tetrahedral voidC. octahedral voidD. trigonal bipyramidal void.
Answer» Correct Answer - C A double triangular void surrounded by 6 spheres is octahedral void.

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