Acta Crystallographica Section B

Structural Science

Volume 56, Part 1 (February 2000)

research papers

Acta Cryst. (2000). B56, 11-16 [ doi:10.1107/S010876819901054X ]

X-ray study of deformation density and spontaneous polarization in ferroelectric NaNO₂

T. Gohda, M. Ichikawa, T. Gustafsson and I. Olovsson

Abstract: The deformation electron density of ferroelectric sodium nitrite has been determined from X-ray diffraction data at 30 K, using Hirshfeld deformation functions. Owing to the strong correlation between odd terms of the deformation coefficients, constraints were imposed in the refinement. The net charges for Na, N and O atoms were estimated to be 0.27, 0.20 and -0.24 e, respectively. The calculated spontaneous polarization using these net charges and atomic dipole terms, 7.8 µC cm^-2, is much closer to the recently measured value, 12 µC cm^-2, as compared with the value calculated from the formal point charges (74 µC cm^-2).

Keywords: ferroelectrics; deformation density; spontaneous polarization.