Re-refinement of sodium ammonium sulfate dihydrate at 170 K.

Tamira Eckhardt,Rüdiger W Seidel,Christoph Wagner,Peter Imming

doi:10.1107/s2414314620012754

Abstract

The title compound, sodium ammonium sulfate dihydrate (SASD), NaNH4SO4·2H2O, a synthetic analogue of the mineral lecontite, is a well known ferroelectric. The crystal structure of the paraelectric phase has been re-refined at 170 K on the basis of single-crystal X-ray data, improving the previous study [Arzt & Glazer (1994 ▸). Acta Cryst. B50, 425-431] in terms of accuracy regarding hydrogen-atom positions and thus details of the hydrogen bonding. O-H⋯O and N-H⋯O hydrogen bonds between the principal building units [Na(OH2)4O2 octa-hedra, SO4 tetra-hedra and ammonium cations] constitute a three-dimensional network structure.

Highlights

The title compound, sodium ammonium sulfate dihydrate (SASD), NaNH4SO4Á2H2O, a synthetic analogue of the mineral lecontite, is a well known ferroelectric
The crystal structure of the paraelectric phase has been re-refined at 170 K on the basis of single-crystal X-ray data, improving the previous study [Arzt & Glazer (1994)
The crystal structure of SASD was first determined by Corazza et al (1967) from equi-inclination Weissenberg photographs at room temperature

Summary

Structure description

The title compound, sodium ammonium sulfate dihydrate (SASD), NaNH4SO4Á2H2O, is the synthetic analogue of the mineral lecontite (Hawthorne et al, 2000), as revealed by Faust & Bloss (1963) through a diffractometry study of both synthetic and natural material. The crystal structure of SASD was first determined by Corazza et al (1967) from equi-inclination Weissenberg photographs at room temperature. Arzt & Glazer (1994) redetermined the crystal structure at room temperature based on serial detector data. Kloprogge et al (2006) reported a Rietveld refinement of the structure of SASD at room temperature, thereby confirming the results of the previous single-crystal X-ray analyses. We have re-refined the crystal structure of the paralectric phase of SASD at 170 K on the basis of single-crystal X-ray diffraction data. Symmetry code: (i) x À 12; Ày þ 32; Àz þ 1. Na1Á Á ÁNa1i and Na1Á Á ÁNa1ii are separated by 3.1317 (2) and 3.1316 (2) A , respectively [symmetry codes: (i) x À 12, Ày + 32, Àz + 1; (ii) x + 12, Ày + 32, Àz + 1]. The sulfate anion exhibits the typical tetrahedral shape with an r.m.s. deviation from exact Td symmetry of only

DÁ Á ÁA

Synthesis and crystallization

Absolute structure parameter

Data collection

Special details