Crystal structure

The correct order of the packing efficiency in different types of unit cells is _______?

• fcc < bcc < simple cubic

• fcc > bcc > simple cubic

• fcc < bcc > simple cubic

• bcc < fcc > simple cubic

Which of the following statements about lattices and unit cells is correct?

• A unit cell contains a whole number of complete molecules

• Lattice points are chosen to lie on atoms.

• Lattice points all have identical surroundings

• Unit cells are constructed by connecting adjacent lattice points to give the largest possible repeat unit.

Consider the Bragg equation. If the value of the wavelength is doubled, which of the following is NOT true?

• Bragg angles of reflections increase.

• The d spacings become smaller.

• The diffraction pattern expands.

• Some previously accessible reflections can no longer be measured.

Repeatable entity of a crystal structure is known as

• Crystal

• Lattice

• Unit cell

• Miller indices

Coordination number for closest packed crystal structure

• 16

• 12

• 8

• 4

Atomic packing factor is

• Distance between two adjacent atoms

• Projected area fraction of atoms on a plane

• Volume fraction of atoms in cell

• None

Coordination number in simple cubic crystal structure

• 8

• 6

• 12

• 10

A family of directions is represented by

• (hkl)

• <hkl >

• {hkl}

• [hkl]

-----------is defined as the no. Of nearest atoms which are directly surrounding given atom

• lattice

• Bravias

• Atomic packing factor

• Co-ordination no.

The number of Bravais lattices is:

• 256

• 7

• 14

• 37