Redetermination of Mg2B25 based on single-crystal X-ray data

Luca Bindi,Luciana Malpezzi,Alessandro Figini Albisetti,Giovanni Giunchi,Norberto Masciocchi

doi:10.1107/s1600536812023768

Abstract

The crystal structure of Mg2B25, dimagnesium pentaeicosaboride, was reexamined from single-crystal X-ray diffraction data. The structural model previously reported on the basis of powder X-ray diffraction data [Giunchi et al. (2006 ▶). Solid State Sci. 8, 1202–1208] has been confirmed, although a much higher precision refinement was achieved, leading to much smaller standard uncertainties on bond lengths and refined occupancy factors. Moreover, all atoms were refined with anisotropic displacement parameters. Mg2B25 crystallizes in the β-boron structure type and is isostructural with other rhombohedral compounds of the boron-rich metal boride family. Magnesium atoms are found in interstitial sites on special positions (two with site symmetry .m, one with .2 and one with 3m), all with partial occupancies.

Highlights

The crystal structure of Mg2B25, dimagnesium pentaeicosaboride, was reexamined from single-crystal X-ray diffraction data
The structural model previously reported on the basis of powder X-ray diffraction data [Giunchi et al (2006)
All atoms were refined with anisotropic displacement parameters

Summary

Data collection

Giunchi,b Luciana Malpezzic and Norberto Masciocchid a Dipartimento di Scienze della Terra, University of Firenze, Via La Pira 4, I-50121. Key indicators: single-crystal X-ray study; T = 298 K; mean (B–B) = 0.001 Å; disorder in main residue; R factor = 0.021; wR factor = 0.049; data-to-parameter ratio = 6.5. The crystal structure of Mg2B25, dimagnesium pentaeicosaboride, was reexamined from single-crystal X-ray diffraction data. The structural model previously reported on the basis of powder X-ray diffraction data [Giunchi et al (2006). All atoms were refined with anisotropic displacement parameters. Mg2B25 crystallizes in the -boron structure type and is isostructural with other rhombohedral compounds of the boron-rich metal boride family. Magnesium atoms are found in interstitial sites on special positions (two with site symmetry .m, one with .2 and one with 3m), all with partial occupancies

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