Engineering Physics

2.14 Calculation of lattice constant

The unit cell edge length of a cubic system is calculated using the density of the crystal. Let ‘a’ be the edge length (or primitive) of a cubic unit cell and ‘ρ’ be the density of the crystal.

The mass of the unit cell = ρa³ _____ (2.1)

 

Let ‘M’ be the molecular weight and N_A be the Avogadro number (i.e., number of molecules per kg mole of the substance) of the crystal.

Then, mass of each molecule =

If each unit cell contains n molecules (or lattice points),

Then the mass of unit cell = n ____ (2.2)

From ...