question_answer

For a cubic crystal structure which one of the following relations indicating the cell characteristic is correct?[AIPMT (S) 2007]

A)  \[a\ne b\ne c\] and \[\alpha \ne \beta \] and \[\gamma \ne {{90}^{o}}\]    

B)       \[a\ne b\ne c\] and \[\alpha =\beta =\gamma ={{90}^{o}}\]

C)       \[a=b=c\] and \[\alpha \ne \beta \ne \gamma ={{90}^{o}}\]

D)       \[a=b=c\] and \[\alpha =\beta =\gamma ={{90}^{o}}\]

Correct Answer: D

Solution :

In cubic crystals, the crystal axes are perpendicular to one another \[(\alpha =\beta =\gamma ={{90}^{o}})\] and the repetitive interval is the same along the three axes \[(a=b=c)\].

Note:    Cubic crystal may be simple, body centred or face centred.