The crystal structure of TlMgCl3 from 290 K to 725 K

Drew R Onken; Didier Perrodin; Sven C Vogel; Edith D Bourret; Federico Moretti

doi:10.1107/S2056989020013201

The crystal structure of TlMgCl₃ from 290 K to 725 K

Acta Crystallogr E Crystallogr Commun. 2020 Oct 6;76(Pt 11):1716-1719. doi: 10.1107/S2056989020013201. eCollection 2020 Nov 1.

Authors

Drew R Onken¹, Didier Perrodin¹, Sven C Vogel², Edith D Bourret¹, Federico Moretti¹

Affiliations

¹ Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
² Los Alamos National Laboratory, Los Alamos, NM 87545, USA.

Abstract

The title compound, thallium magnesium trichloride, has been identified as a scintillator with both moderate gamma-stopping power and moderate light yield. Knowledge of its crystal structure is needed for further development. This work determines the crystal structure of TlMgCl₃ to be hexa-gonal P6₃/mmc (No. 194) and isostructural with RbMgCl₃, contrary to previously reported data. This structure was obtained by single-crystal X-ray diffraction and was further confirmed by neutron diffraction measurements. Extending neutron diffraction measurements to high temperature, the data show that TlMgCl₃ maintains this crystal structure from 290 K up through 725 K, approaching the melting point of 770 K. Anisotropic thermal expansion coefficients increase over this temperature range, from 31 to 38 × 10^-6 K^-1 along the a axis and from 19 to 34 × 10^-6 K^-1 along the c axis.

Keywords: TlMgCl3; crystal structure; high-temperature neutron diffraction; scintillator.

Grants and funding

This work was funded by U.S. Defense Threat Reduction Agency (DTRA) grant HDTRA19-31194 to Lawrence Berkeley National Laboratory (LBNL) authors. U.S. Department of Energy, National Nuclear Security Administration (NNSA), Office of Defense Nulear Nonproliferation (DNN) grant AC02-05CH11231 to LBNL authors. U.S. Department of Energy, NNSA grant 89233218NCA000001 to Los Alamos National Laboratory (LANL).