(70cz) The Effects of Impurities on Crystal Morphology Formation: an Experimental and Molecular Modelling Investigation

It has been recognized that different crystal morphologies can be formed by adding impurities. However, a quantitative understanding is lacking on how the impurities change the crystal shape and/or size. KDP crystallisation is chosen in this study because of the almost- perfect shape and manageable size (~ 1 cm) of KDP crystals. It is found that in forming KDP crystals, by adding trivalent metal ion groups, the crystal shape is elongated by about 80 % (but depending on concentration). Our previous study speculated that the trivalent metal ion groups were preferably adsorbed on the (100) face, subsequently the ion groups inhibited the crystal growth on these faces, and crystal growth were dominated by electrostatic potential of impurity and crystal faces. In this contribution, various chelate agents, which have different number of carbonic acid, are used for examining the effect of electrostatic potential of impurity on its adsorption onto crystal faces. Computational simulations employing Gaussian method are performed to provide insight on the impurity adsorption and the subsequent effect on crystal morphology formation. Simulation results are verified by our experimental results on KDP crystal growth.