if molecular formulae is A2B then find the percentage of octahedral and tetrahedral voids if cations A are equally distributed between octahadral and tetrahedral voids and anions B are in CCP. kindly reply quick a request.

Asked by Farooq Ahmad Shah | 1st Jun, 2015, 08:15: PM

Expert Answer:

In the given CCP lattice, anions B are in CCP.
In a CCP structure, the number of octahedral voids = number of atoms and number of tetrahedral voids = 2 × number of octahedral voids.

Effective number of atom in CCP = 4 = octahedral void 
octahedral void × 2 = tetrahedral void = 8 

Hence, if 1 A is in tetrahedral void while 1 A is in octahedral void. 
Thus for each tetrahedral void, there will double octahedral viods are filled.
That means for 4 octahedral voids, 8 tetrahedral voids are occupied.
Hence, octahedral voids are 100% occupied while tetrahedral voids are 50% occupied.

Answered by Prachi Sawant | 4th Jun, 2015, 10:55: AM