A unit cell of diamond is a cube of side A, with carbon atoms at each corner, at the center of each face and, in addition, at positions displaced by .25*A*(i+j+k) from each of those already mentioned; i, j, k are unit vectorsalong the cube axes. One corner of the cube is taken as the origin of coordinates. What are the vectors joining the atom at .25*A*(i+j+k) to its four nearest neighbors? Determine the angle between the carbon bonds in a diamond.