In an CCP crystal of metal M (diameter = a oversetoA ), we are trying to dope two smaller elements X ( radius =0.16a oversetoA ) and/or Y (radius =0.25a oversetoA ) without disturbing M-M contact, then select correct matching.

Question

In an CCP crystal of metal M (diameter = a oversetoA ), we are trying to dope two smaller elements X ( radius =0.16a oversetoA ) and/or Y (radius =0.25a oversetoA ) without disturbing M-M contact, then select correct matching. (A)

(B)

(C)

(D)

Tardigrade Admin · Accepted Answer

(rX/rM)=(0 . 16 a/0 . 5 a)=0.32, so X can occupy only O- Voids (ideal rr is 0.414 ) but not T- void (ideal rr is 0.225 ) and (rX/rM)=(0 . 25 a/0 . 5 a)=0.5, Y can't occupy either O- voids or T- voids. On doping X atoms in O- voids, Packing fraction as well as density of crystal will increase as dimensions do not change (no distubing of M-M contact allowed) but total mass increases in the unit cell (we cant comment about X being heavier than M atoms).

Q. In an CCP crystal of metal M (diameter = aAo ), we are trying to dope two smaller elements X ( radius =0.16aAo ) and/or Y (radius =0.25aAo ) without disturbing M−M contact, then select correct matching.

Q. In an $CCP$ crystal of metal $M$ (diameter = $a A o$ ), we are trying to dope two smaller elements $X$ ( radius $= 0.16 a A o$ ) and/or $Y$ (radius $= 0.25 a A o$ ) without disturbing $M - M$ contact, then select correct matching.