Lattice Dynamics in Organic Ferroelectrics Using Neutron Spectroscopy and Ab-Initio Modeling

Lattice dynamics in organic ferroelectric PhMDA (2-phenylmalondialdehyde C9H8O2) has been investigated using inelastic neutron scattering (INS) spectroscopy and first principles based calculations. Most of the prominent features of the INS spectrum originated from the normal modes of hydrogen bonded malondialdehyde (MDA) units rather than from phenyl rings. It is also found that carbon-hydrogen bonds in the MDA unit are tighter than these in phenyl rings. From the calculated splitting of LO (longitudinal optical) and TO (transverse optical) normal modes, it is predicted that hydrogen bonds in MDA units, which hold the solid state structure, contribute more to the ferroelectric polarisation of PhMDA. Any distortion of H-ions in these hydrogen bonds thus affects ferroelectric properties of this material.

Automated summary

Lattice dynamics in organic ferroelectric PhMDA have been studied using inelastic neutron scattering (INS) spectroscopy and first principles calculations. The INS spectrum's prominent features are mainly from the normal modes of hydrogen bonded malondialdehyde units instead of phenyl rings. It is predicted that hydrogen bonds in the malondialdehyde units contribute more to the ferroelectric polarization of PhMDA, and any distortion of H-ions in these hydrogen bonds affects the material's ferroelectric properties.