Spontaneous polarization and piezoelectricity in polar molecular crystals

Molecular materials with a polar arrangement of the constituent dipoles are good candidates for exhibiting piezoelectric properties, directly related to the \mbox{strain-induced} polarization. The \mbox{metal-organic} molecular crystal (4-dimethylaminopyridyl)bis(acetylacetato)zinc(II) (ZNDA) has been investigated from first principles. The spontaneous polarization and the piezoelectric properties have been studied by means of the modern theory of polarization, focusing on the relation between the piezoelectric properties of the organic crystal and the electronic properties of the polar molecule.