FIDAP simulation of the F color centers formation in alkali halides crystals using additive method of crystals coloring

In this paper we have performed a numerical simulation of the additive coloring of the crystals by solving the time dependent diffusion equation. The finite element commercial code FIDAP has been used for the numerical modeling. The numerical results are in agreement with the experimental measurement and show that, after an exposure to the vapor of 30 minutes, the coloration of a KCI crystal, with the dimensions 2 mm x 2 mm x 20 mm and with the diffusion constant D = 8 x 10(-6) cm2/s at temperature T = 600 K, becomes very uniform. A numerical optimization of the coloration time for a two-dimensional (2D) and three-dimensional (3D) geometry is performed. The excellent agreement between the 3D numerical results and the experimental measurement shows that the 3D simulation is more realistic than the 2D case.