The nucleation parameters, such as interfacial tension, radius of the critical nucleus and critical free energy change have been estimated for deuterated L-arginine phosphate (dLAP), potassium fluoride mixed dLAP and sodium azide mixed dLAP single crystals. Pure and additive mixed dLAP single crystals are grown by slow cooling technique. The effect of microbial contamination and colouration on the growth solutions has been studied. The crystalline powder of the grown crystals has been examined by X-ray diffraction and thermal analyses in order to estimate the lattice parameters and study thermal properties respectively. (C) 2002 Elsevier Science B.V. All rights reserved.