Laboratory parallel-beam transmission X-ray powder diffraction investigation of the thermal behavior of calcite: comparison with X-ray single-crystal and synchrotron powder diffraction data

Thermal behavior of calcite has been analyzed in the 303-1098 K thermal range by laboratory parallel-beam transmission X-ray powder diffraction. Present results provide a clear indication of the possibility to extract high-quality structural data from such instrumental set up. Such quality has been proved to be at the same level of a mid eighties X-ray single crystal investigation. Analysis of the spontaneous strain e(33) provides a critical exponent beta of 0.2499(5) consistent with the value of 1/4 expected for a tricritical behavior. Structure refinements seemengly support the Ising model of disorder.