The paper describes an analysis of 400 mm diameter Si Czochralski growth with applied direct current magnetic fields of different configurations and strengths, using 3D unsteady numerical simulation. The numerical model is based on the Navier-Stokes equations coupled to heat transfer and electric current flow in the crystallization zone, including the calculation of the crystallization front geometry. The obtained results are discussed with regard to study optimal crystal growth parameters providing dislocation free crystal growth with a low vacancy concentration. (c) 2007 Elsevier B.V. All rights reserved.