This example is to demonstrate how to set up a user-defined growth rate model for grain growth simulation. In this example, the built-in growth model can be replaced by the user-defined variable “Growth_Rate”. In the built-in growth model, the growth rate is given by Eq. 1~Eq. 4, and it can be replaced by the expression value="KP(@Grain)/2.86e-10*2*0.75*7.1e-6/s(@Grain)" where “KP(@Grain)” is to get the effective atomic mobility calculated from mobility database and “s(@Grain)” is to get the average grain size. The grain boundary width is “2.86e-10”, grain boundary energy is “0.75” and molar volume is “7.1e-6”. Below is the kdb defining the grain growth model