Vertical Bridgman growth of GeSi alloy with an average Si composition of 15 atom% was performed on a large 25 mm diameter by 90 mm long melt volume to significantly increase the buoyancy-driven convection within the melt. For one sample, the longitudinal Si composition along the sample length is described by a simple one-dimensional model including complete mixing of the Ge and Si melt constituents and the equilibrium Si segregation coefficient given by the GeSi phase diagram. The excellent agreement between theory and experiment shows that the GeSi phase diagram in the Ge-rich region is determined accurately. (C) 2011 Elsevier B.V. All rights reserved.