Nearest neighbour distance

First three nearest neighboure distance for primitive cubic lattice are respectively (edge length of unit cell = a):

First three nearest neighbout distance for body centrered cubic lattice are

Lithium crystallizes in a body centred cubic lattice. How many next-nearest neighbours does each Li have?

In a face-centred cubic crystal, the neighbour distance is …… times the edge of the crystal.

Iron crystallizes in several forms. At 1185 K , the body centred cubic alpha - form of iron changes to the face centred cubic gamma - form of iron. Assuming that the distance betweem the nearest neighbours is the same in two forms at the transition temperature, calcuate the ratio of the density of alpha - form to that of gamma - form at the transition temperature.

The number of nearest neighbours and next nearest neighbours of an Na^(o+) ion in a crystal of NaCl are, respectively,