# Solution to Exercise 3.1-1: "Calculate Geometry Factors" The geometry factor (always for a single vacancy) was defined as
g  =  ½ · Si æ ç è ö ÷ ø With Dxi = component of the jump in x-direction. Looking at the fcc lattice we realize that there are 12 possibilities for a jump because there are 12 next neighbors. 8 of the possible jumps have a component in x (or – x ) -direction, and Dxi = a/2 We thus have
g fcc  =  ½ · æ ç è ö ÷ ø Looking at the bcc lattice we realize that there are 8 possibilities for a jump because there are 8 next neighbors. All 8 possible jumps have the component Dxi = a/2 in x-direction, again we have
g bcc  =  ½ · æ ç è ö ÷ ø Looking at the diamond lattice we realize, after a bit more thinking (or drawing, or looking at a ball and stick model), that there are 4 possible jumps. All 4 jumps have the component Dxi = a/4 in x-direction, and we obtain
g diamond  =  ½ · æ ç è ö ÷ ø Lattice and Crystal Ionic Crystals Exercise 3.1-1: Calculate the Geometry Factor Exercise 3.3-1 Quick Questions

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