R. Lu et al., THERMODYNAMIC PROPERTIES OF FERROMAGNESIUM SILICATE PEROVSKITES FROM VIBRATIONAL SPECTROSCOPY, J GEO R-SOL, 99(B6), 1994, pp. 11795-11804
Infrared (IR) reflectance and absorbance spectra obtained from polycry
stalline and single-crystal perovskites of MgSiO3 and (Mg0.9Fe0.1)SiO3
compositions yielded virtually all the expected fundamental modes. Ne
ar-IR absorbance spectra indicate that the polycrystals were anhydrous
, whereas the single crystal contained about 0.06 wt % H2O. A Kieffer-
type model was used to calculate heat capacity, entropy, and Debye tem
perature for the orthorhombic perovskite phase. The calculated values
at 298 K are Cp = 82+/-2 J/mol K and S = 56+/-2 J/mol K. Our calculate
d Cp agrees with calorimetric data within 5%. Above 500 K, the Debye t
emperature is nearly constant and equals 960+/-30 K. The bulk modulus
is calculated from vibrational frequencies to be 265+/-13 GPa which li
es within 2% of recent experiments. The Clapeyron slope for the phase
transition between ilmenite and orthorhombic perovskite is calculated
to be 1.1+/-0.6 MPa/K which is close to the experimental determination
.