Lattice dynamics and elasticity of SrCO₃

Abstract

The lattice dynamics and elasticity of synthetic SrCO3 have been investigated by a combination of ab initio lattice dynamics calculations, microcalorimetry, Raman spectroscopy, X‐ray thermal diffuse scattering and high‐resolution inelastic X‐ray scattering. The results of density functional based calculations were in all cases in good agreement with experiment. For the spectroscopic investigations, peak positions and intensities are well reproduced by the density functional theory model. Experimentally determined intensity distributions in thermal diffuse scattering maps differ from the theoretical distribution only in the (HK0) plane, a fact that is attributed to stacking disorder. As the model is accurate and reliable, the complete elastic stiffness tensor is predicted and, on the basis of these results, the anisotropy of the sound velocities is discussed, also in relation to the anisotropy in other carbonate systems.

Single-crystal elasticity of SrCO3 by Brillouin spectroscopy

“…Due to the orientation of the three platelets, our dataset of Brillouin scattering measurements lacks measurements in directions belonging to (100) and (010) crystallographic planes. This limits the constraints on the coefficients c 13 , c 23 and c 33 . In order to reduce the uncertainties on these constants we added to the original Brillouin dataset the results of IXS measurements [13] of the longitudinal acoustic phonon dispersion curve in the crystallographic z-direction, which constrain the coefficient c 33 .…”

“…Strontianite has an orthorhombic crystal structure with space group Pmcn [28]. Hence, the elastic stiffness tensor c ij has 9 independent non-zero tensor components which are c 11 , c 12 , c 13 , c 22 , c 23 , c 33 , c 44 , c 55 and c 66 in contracted Voigt notation. The complete velocity data set was used to determine the coefficients of the elastic tensor.…”

“…Full geometry optimisations were carried out until forces were smaller than 0.01 eV/Å and no component of the stress tensor exceeded 0.02 GPa. The accuracy of this approach has previously been established by comparison of computed structural and physical parameters at ambient pressure to experimental data [13].…”

“…In contrast, the elasticity of aragonite-group minerals has been investigated only in two experimental studies of natural aragonite: Voigt [11], who determined the elastic coefficients with ultrasonic interferometry and Liu et al [12], who measured the elastic coefficients with Brillouin spectroscopy. Recently, all tensor components of SrCO 3 have been predicted based on density functional theory, DFT, calculations [13]. The study of Nguyen-Thanh et al [13] was complemented with high resolution inelastic xray scattering experiments to obtain the c 33 tensor component.…”

“…Recently, all tensor components of SrCO 3 have been predicted based on density functional theory, DFT, calculations [13]. The study of Nguyen-Thanh et al [13] was complemented with high resolution inelastic xray scattering experiments to obtain the c 33 tensor component. However, without further experimental data these results cannot be benchmarked against experiment.…”