• journal_title：American Mineralogist
• Contributor：Yu Ye ; Joseph R. Smyth ; Paul Boni
• Publisher：Mineralogical Society of America
• Date：2012-
• Format：text/html
• Language：en
• Identifier：10.2138/am.2012.3923
• journal_abbrev：American Mineralogist
• issn：0003-004X
• volume：97
• issue：4
• firstpage：707
• section：Articles

Crystal structures of four aragonite-group carbonates—aragonite (Ca_0.997Sr_0.003CO₃), calcian strontianite (Ca_0.147Sr_0.853CO₃), cerussite (Ca_0.001Pb_0.999CO₃), and witherite (Sr_0.019Ba_0.981CO₃)—have been refined at ambient conditions, and thermal expansion has been measured over a range of temperatures from 143 to 586 K by single-crystal X-ray diffraction. Average linear thermal expansion coefficients α₀(V) are 58(2), 58.3(7), 64(2), and 57(2) (× 10⁻⁶ K⁻¹) for aragonite, strontianite, cerussite, and witherite, respectively, throughout the experimental temperature range. Aragonite, strontianite, and witherite have very similar α₀(V) values, whereas that of cerussite is significant larger, primarily due to the c-axis thermal expansion for cerussite being much larger than those of the other carbonates. There are no significant differences for α₀(a) values among the four carbonates, whereas α₀(b) values decrease in the order of aragonite > strontianite > cerussite ≈ witherite, and α₀(c) values increase in the order of aragonite < strontianite < witherite < cerussite. Crystal structures were refined for aragonite (184 to 527 K). <Ca-O> vs. T (K) is fitted linearly quite well, with a slope of 5.8(8) × 10⁻⁶ (Å/K). Corrected for assumed rigid body motion, the CO₃ groups showed no significant change in C-O distances over the temperature range.