  We study the ground state quantum phase diagram for a two species Bose
mixture in a one-dimensional optical lattice using the finite size density
matrix renormalization group(FSDMRG) method. We discuss our results for
different combinations of inter and intra species interaction strengths with
commensurate and incommensurate fillings of the bosons. The phases we have
obtained are superfluid, Mott insulator and a novel phase separation, where
different species reside in spatially separate regions. The spatially separated
phase is further classified into phase separated superfluid(PS-SF) and Mott
insulator(PS-MI). The phase separation appears for all the fillings we have
considered, whenever the inter-species interaction is slightly larger than the
intra-species interactions.
