  We present results from ab initio calculations based on density functional
theory for bismuth-based double perovskite Bi2MnTiO6. Using total energy
calculation with stress and force minimization we have predicted the
equilibrium crystal structure for Bi2MnTiO6 considering potential structures
into the calculation. We have predicted that the ground state of Bi2MnTiO6 will
be a noncentrosymmetric rhombohedral structure with space group R3c. Our spin
polarized calculation for different possible collinear magnetic configurations
we found that Bi2MnTiO6 will be an insulator with G-type antiferromagnetic
ordering in its ground state. The coexistence of both stereochemically active
Bi-6s lone pair and the Ti4+ with d0-ness which bring covalency results in the
stabilization of noncentrosymmetric structure and thus ferroelectricity. Our
orbital projected density of states plot shows that the Mn2+ in Bi2MnTiO6 will
be at high spin state with a spin moment of 4.28 {\mu}B. Hence Bi2MnTiO6 is
predicted to be a magnetoelectric material.
