Search for a ferroelectrically ordered form of ice VII by neutron diffraction under high pressure and high electric field

Abstract

Neutron diffraction experiments of ice VII at pressures up to 6.2 GPa and 10.2 kV/mm were conducted to investigate the potential ferroelectrically ordered structure of ice VII induced by a high electric field. To accomplish this, we developed a high-pressure cell assembly to allow for powder neutron diffraction to be conducted under both high-pressure and high-electric field conditions. However, the subsequent observed diffraction patterns taken in situ at these conditions do not show sufficient evidence of the proposed ferroelectrically ordered structure of ice VII. We estimate the degree of the hydrogen ordering in ice VII under the applied conditions from high-pressure $P\ensuremath{-}E$ loop measurements, and discuss the future possibilities of detecting the ferroelectrically ordered structure.