The structure, optical activity and spontaneous polarisation of the room-temperature phase of dicalcium lead propionate

Abstract

The room-temperature structure of ferroelectric dicalcium lead propionate, DLP, has been determined: it is tetragonal with space group P41(C42) or P43(C44) with a=12.510(3) AA, c=17.314(2) AA, z=4. One of the six independent propionate groups in the structure is found to have its methyl carbon statistically disordered in two sites. The spontaneous polarisation, Ps, is calculated from the state shifts of the Pb, Ca and O atoms (relative to the high-temperature paraelectric phase). The DLP crystals of space group P41 are found to be aevorotatory, as in the case of the similar compound dicalcium strontium propionate (DSP).