Clarification of Impurity Colouring and Adsorption Mechanism for KDP Crystal Growth by Computational Chemistry

Yusuke ASAKUMA*, Kouji MAEDA and Keisuke FUKUI

Department of Mechanical and Systems Engineering, University of Hyogo
2167 Shosha Himeji Hyogo Japan 671-2280

(Received: September 7, 2007; Accepted for publication: November 20, 2007; Advance publication: January 18, 2008)

Impurity effect of KDP(KH2PO4 crystal growth by trivalent metal ion in solution is reasonably well documented. If the metal ion is adsorbed onto the crystal surface, it prevents the step propagation relevant to the crystal growth rate. Although a recovery effect of the metal ion adsorption was discovered in our recent work on the addition of chelate agents, the impurity effect and recovery mechanisms are not clearly understood both theoretically and phenomenally. Moreover, the dye compound in solution can colour the KDP crystal. However, dyes are segregated in specific growth sectors due to crystal anisotropy. The mechanism of the dye selectivity and the orientation of the adsorbed dye are also not clear. Accordingly, the impurity effect by metal ion, recovery effect by chelate and colouring mechanism by dye about the KDP crystal were investigated by computational chemistry in this study. It was found that these behaviors could be explained by electrostatic potential (ESP) distribution.

Keywords: Molecular orbital method, KDP crystal, Electrostatic potential

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