Open AccessCrystal structure of Ca2Na2(CO3)3 (shortite)
Author(s) -
Brian Dickens,
Anthony Hyman,
W. E. Brown
Publication year - 1971
Publication title -
journal of research of the national bureau of standards. section a. physics and chemistry
Language(s) - Uncategorized
Resource type - Journals
eISSN - 2376-5704
pISSN - 0022-4332
DOI - 10.6028/jres.075a.013
Subject(s) - orthorhombic crystal system , crystallography , ion , chemistry , crystal structure , group (periodic table) , crystal (programming language) , absorption (acoustics) , extinction (optical mineralogy) , physics , mineralogy , optics , organic chemistry , computer science , programming language
Ca 2 Na 2 (CO 3 ) 3 crystallizes in the orthorhombic unit cell a = 4.947(1) Å, b = 11.032(2) Å, and c = 7.108(1) Å at 25 °C with two formula weights in space-group Amm2. The structure has been redetermined, corrected, and refined to R w = 0.025, R = 0.020 using 684 "observed" x-ray reflections from a single crystal. Corrections were made for absorption and isotropic extinction. In the extinction refinements, r refined to 0.00017(1) cm. The structure consists of Ca 2 NaCO 3 layers interleaved with Na(CO 3 ) 2 layers. The Ca ion is coordinated strongly to nine oxygens, including three CO 3 edges, with Ca … O distances varying from 2.401(2) Å to 2.576(2) Å. One Na ion is coordinated strongly to eight oxygens, including two CO 3 edges, with Na … O distances from 2.429(2) Å to 2.605(1) Å. The other Na ion is coordinated strongly to six oxygens, including one CO 3 edge, at 2.296(1) Å to 2.414 Å, and weakly to a seventh at 3.050(3) Å. One CO 3 group is coordinated to seven cations, the other is coordinated to eight. The CO 3 groups have seemingly maximized their edge sharing with Ca ions rather than Na ions.