Monoxyde PbOα(II): Élasticité et vibrations anisotropes; modélisation; constantes élastiques
Abstract
Using low temperature neutron diffraction data, the structural evolution of the layered compound PbOα is interpreted. The anisotropic Debye temperatures are evaluated from Bii (Å 2) temperature factors: θa = 350 K θc = 239 K. Using the Debye model, mean force constants are calculated taking into account the Grüneisen relations. A simple model permits calculation of the anisotropic compressibility factors ( χa ∼ 0.47 × 10 -11 Pa -1, χc ∼ 1.26 × 10 -11 Pa -1), and the Grüneisen constants ( γa = 1.22, γc = 1.05). Thermodynamic and structural approximations are needed; therefore, the proposed model can be extended at all uniaxial structures. The elastic constants sij (Pa -1) can be obtained by fitting calculated functions αa( T) and αc( T) to the experimental thermal expansion functions αa (obs.) αc (obs.) in the full range 2-300 K: s11 + s12 = 0.78 × 10 -11 Pa -1, s13 = -0.32 × 10 -11 Pa -1, and s33 = 1.9 × 10 -11 Pa -1.
- Publication:
-
Journal of Solid State Chemistry France
- Pub Date:
- June 1985
- DOI:
- 10.1016/0022-4596(85)90271-3
- Bibcode:
- 1985JSSCh..58...87G