Piezoelectric Cs2S2O6: Room temperature crystal structure

Abstract

Cesium dithionate, Cs2S2O6, is moderately strongly piezoelectric at room temperature and crystallizes in the hexagonal system with space group P63mc and two formula units in the unit cell. The lattice constants at 298 K are a=6.356 58±0.000 04 and c=11.539 07±0.000 04 Å (λCuKα1=1.5405 98 Å). The integrated intensities of most reflections with (sin ϑ)/λ?1.08 or 1.15 Å−1 were measured using two crystals and diffractometers. The first crystal gave a total of 1116 independent Fmeas, the second gave two separate sets of structure factors: 415 Fmeas with the crystal having received more radiation exposure than the first crystal and a further 431 Fmeas with still greater radiation exposure. The crystal structure was solved from the Patterson function and Fourier series and refined by the method of least squares. The final agreement factor R=0.033 for the first set, 0.049 and 0.060 for the second two sets of Fmeas. The crystal undergoes x-irradiation damage, with some reflections decreasing in integrated intensity by more than a factor of two. Normal probability plot analysis is used to compare the sets of Fmeas and resulting structural parameters. Redistribution of the Cs+ ions along the trigonal axes is likely, with compensating rearrangement of the S2O6−2 ions. The S2O6−2 ion has a staggered configuration close to 3̄m symmetry, with S–S=2.112±0.003, mean S–O=1.454±0.002 Å in length and S–S–O angle of 104.3±0.2 °, O–S–O=114.1±0.2 °. The two independent Cs+ ions are each nine-coordinated, with average Cs–O=3.231 Å. Layers with stoichiometric composition form normal to the polar axis.