High pressure iso-structural phase transition in BiMn2O5.

The high pressure behavior of multiferroic BiMn2O5 has been investigated using powder x-ray diffraction and Raman scattering techniques as well as density functional theory based first principles calculations. Our investigations show a reversible iso-structural phase transition in BiMn2O5 above 10 GPa. The compressibility along the c axis, i.e. along the edge-shared distorted Mn(4+) octahedral chains, has been found to be significantly reduced above this phase transition, suggesting a dominant role of the relatively rigid Mn-O framework in the high pressure phase rather than that of the coordination sphere around the Bi atom. Bader charge analysis of the charge densities obtained from first principles calculations shows partial atomic charge redistribution among Bi(3+) and Mn(3+) atoms across the phase transition which could be the probable cause of this phase transition.