Pb-driven anti-ferroelectric phase in Pb(Mg1/3Nb2/3)O3 : First-principle study

Density functional calculations are used to investigate the role of Pb displacement in the formation of anti-ferroelectric phase in Pb(Mg1/3Nb2/3)O3. Order and disordered supercells, both are used. Through geometry optimization without symmetry imposed, the two supercells are found to be anti-ferroelectric. Displacement of cations are analyzed and it is shown that asymmetry of Pb's next-nearest B-site shell is probably the reason for anti-parallel displacement of Pb. A-B-site, B-site-O bond distances and O6 octahedral volumes are also calculated.