**(1)**2D square close packing sheets are involved to generate

**simple cubic cell**as well as body centred cell. In which each corner atom is touching potion with its adjacent corner atom.

**(2)**Take two 2D square close packing sheet and Placing a second square packing layer (sheet) directly over a first square packing layer forms a

**"simple cubic"**structure.

**(3)**The simple “cube” appearance of the resulting unit cell is the basis for the name of this three dimensional structure.

**(4)**This packing arrangement is often

**symbolized as "AA..."**, the letters refer to the repeating order of the layers, starting with the bottom layer.

**(5)**The coordination number of each lattice point is six. This becomes apparent when inspecting part of an adjacent unit cell.

**(6)**The unit cell contain eight corner spheres, however, the total number of spheres within the unit cell is 1 (only 1/8th of each sphere is actually inside the unit cell). The remaining 7/8ths of each corner sphere resides in 7 adjacent unit cells.

**(7) PACKING**

**EFFICIENCY**

**):**

**In simple cubic unit cell:**

**(1)**Let ‘a’ be the edge length of the unit cell and r be the radius of sphere.

**(2**) As sphere are touching each other therefore a = 2r

**(3)**No. of spheres per unit cell = 8*1/8=1

**(4**) Volume of the sphere =

**4/3(pi) r**

^{3}**(5)**Volume of the cube = a

^{3}= (2r)

^{3}= 8r

^{3}

**(6) Packing efficiency (space occupied):**

**(7) Density of simple unit cell:**

**(8) Coordination Number:**

**(1)**The nearest neighbour distance is just the lattice parameter

**(a)**therefore coordination number for a given atom in SCC unit cell is

**6 (six)**.

**(2)**The next nearest neighbour are

**12**at distance

**a/root 2**(each face diagonal in x ,y and Z plane).

**(3)**3

^{rd}neighbour (Next to Next nearest neighbour) are

**(8)**at distance

**a root 3**(each corner along body diagonal.

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