Ab initio studies of stepped {100} surfaces of KDP crystals

Potassium dihydrogen phosphate (KH2PO4, KDP) crystals have important uses in laser components and are grown in large scale for that purpose. The need for habit control has led to interest in the step-pinning mechanisms that cause growth inhibition of the {100} face. Model systems representing five stepped KDP {100} surfaces are prepared and studied using ab initio quantum methods. Results of Hartree-Fock and density functional theory plane-wave calculations are presented, including estimated energies of ion and column removal for the steps. Steps terminated by phosphate ions are found to be less energetically favorable than their potassium-terminated counterparts. In addition, surface layer removal energies for the {100} face and the potassium-bounded and phosphate-bounded {101} faces are reported. The potassium-bounded {101} face is found to have a greater surface removal energy than the unexpressed phosphate-bounded {101} face. (C) 2004 Wiley Periodicals, Inc.