Question

Cu is in FCC structure. We know that even at close to melting temperature, vacancies are still sparsely distributed, i.e., it is almost impossible to find two vacancies directly adjacent to each other. So, for a single vacancy (assuming that it is at the origin (0,0,0) of FCC structure), determine (1) How many Cu atoms (nearest neighbors) can directly jump to this vacancy

Answer 1

6

Step-by-step explanation:

FCC is face centered cubic lattice. In FCC structure, there are eight atoms at the eight corner of the cubic unit cell and one atom centered in each of the faces. FCC unit cells consist of four atoms, (8/8) at the corners and (6/2) in the faces.

Given that, Cu has FCC structure and it contains a vacancy at origin (0, 0, 0). And there is no other vacancy directly adjacent to the vacancy at the origin. So, all the adjacent positions contain Cu atoms. Hence, the total number of adjacent atoms of the vacancy at origin can jump into this vacancy.

the above FCC unit cell clearly indicates that there are six adjacent atoms adjacent to the vacancy at origin

So, the total number of adjacent atoms of the vacancy at origin can jump into this vacancy is 6.