Solid State

- Atoms of C form an hcp lattice, which means C atoms are arranged in hexagonal close packing.
- In an hcp lattice, each unit cell contains 2 atoms of C. Thus, there are 2 atoms of C per unit cell.
- Atoms of A occupy 50% of octahedral voids. The number of octahedral voids in an hcp unit cell is equal to the number of atoms of C, which is 2. Therefore, the number of A atoms in the unit cell is 2.
- Atoms of B occupy of the tetrahedral voids. The number of tetrahedral voids in an hcp unit cell is 8. So, the number of B atoms in the unit cell is , approximately 5 atoms of B.
Therefore, the molecular formula of the solid is A B C .