The sound velocity properties of single-crystal rhodochrosite
(MnCO3) were determined up to 9.7 GPa at ambient temperature
by Brillouin scattering spectroscopy. Six elastic constants were
calculated by a genetic algorithm method using the Christoffel’s
equations at each pressure. The elastic constants increased
linearly as a function of pressure and its pressure derivatives ∂Cij/
∂P for C11, C33, C44, C12, C13, C14 were 5.86 (±0.36), 3.82 (±0.44),
2.06 (±0.39), 5.07 (±0.27), 5.34 (±0.44), 1.52 (±0.24), respectively.
Based on the derived elastic constants of rhodochrosite, the
aggregate adiabatic bulk and shear moduli (Ks and G) were
calculated using the Voigt-Reuss-Hill averages and the linear
fitting coefficients (∂Ks/∂P)T and (∂G/∂P)T were 5.05(±0.26) and 0.73
(±0.05), respectively. The aggregate Vp of rhodochrosite increased
clearly as a function of pressure and its pressure derivative ∂Vp/∂P
was 7.99(±0.53) × 10−2 km/(s GPa), while the aggregate Vs
increased slowly and ∂Vs/∂P was only 1.19(±0.12) × 10−2 km/
(s GPa). The anisotropy factor for As of rhodochrosite increased
from ∼40% at 0.8 GPa to ∼48% at 9.7 GPa, while Ap decreased
from ∼19% to ∼16% at the corresponding pressure.