The investigation of intra framework substitution of Si by group V transition metals (V, Nb, Ta) is an important strategy to modify or to tune the catalytic properties of zeolites. Theoretically one of the limitations is the size of the zeolite unit cell. In this study the energy and geometry of silicate BEA modified with group V metals is investigated and compared with the results obtained for smaller zeolite models, in particular the SOD structure. The group V substituted T framework sites in BEA zeolite structure with T = O and/or T-OH groups are confirmed: i.e. T = O for T = vanadium, and T-OH for T = niobium or tantalum. (C) 2011 Elsevier B.V. All rights reserved.