text: In lone-pair-active multiferroics, the ferroelectric displacement is driven by the A-site cation, and the magnetism arises from a partially filled d shell on the B site. Examples include bismuth ferrite, BiFeO, BiMnO (although this is believed to be anti-polar), and PbVO. In these materials, the A-site cation (Bi, Pb) has a so-called stereochemically active 6s lone-pair of electrons, and off-centering of the A-site cation is favoured by an energy-lowering electron sharing between the formally empty A-site 6p orbitals and the filled O 2p orbitals.