Open AccessRefinement of the crystal structure of the aragonite phase of CaCO3
Author(s) -
Brian Dickens,
J. S. Bowen
Publication year - 1971
Publication title -
journal of research of the national bureau of standards. section a. physics and chemistry
Language(s) - English
Resource type - Journals
eISSN - 2376-5704
pISSN - 0022-4332
DOI - 10.6028/jres.075a.004
Subject(s) - aragonite , crystallography , crystal structure , group (periodic table) , plane (geometry) , crystal (programming language) , phase (matter) , ion , materials science , unit (ring theory) , chemistry , mineralogy , geometry , mathematics , calcite , organic chemistry , computer science , programming language , mathematics education
Aragonite (CaCO 3 ) crystallizes in the unit cell a = 4.9598(5) Å, b = 7.9641(9) Å, and c = 5.7379(6) Å at 25 °C with four formula weights in space-group Pmcn . The structure has been refined to R w = 0.024, R = 0.040 using 765 x-ray reflections from a single crystal. The Ca ion is coordinated to nine oxygens with Ca … O distances in the range 2.414(2) Å to 2.653(1) Å. The two unique C-O distances in the CO 3 group are 1.288(2) Å (on the mirror plane) and 1.283(1) Å. The two unique O-C-O angles are 119.6(2)° (across the mirror plane) and 120.13(8)°. The distances and angles in the CO 3 group are not significantly different at the 95 percent confidence level.