Commercially available gases contain residual impurities leading to a background oxygen partial pressure of typically several 10(-6) bar, independent of temperature. This oxygen partial pressure is inappropriate for the growth of some single crystals where the desired oxidation state possesses a narrow stability field. Equilibrium thermodynamic calculations allow the determination of dynamic atmosphere compositions yielding such self-adjusting and temperature dependent oxygen partial pressures, that crystals like ZnO, Ga2O3, or Fe1-xO can be grown from the melt. (C) 2008 Elsevier B.V. All rights reserved.