Determination of elastic constants of benzalazine from thermal diffuse scatterings of X-rays

Abstract

All the nine elastic constants of an orthorhombic single crystal of benzalazine have been determined by photographic methods from the measurements of the intensities of thermal diffuse scattering observed in the Laue photographs taken with monochromatized Cu Kα radiation having no higher harmonics. The direct-beam intensity was determined by reducing it by a factor of 10^-8 through absorption in nickel foils of known thickness. The regions of reciprocal space near reciprocal lattice points 602, 022, 002, 600, 710 and 260 were investigated. Corrections were applied to diffusely sesttered intensities for general scattering, polarization and skew factors. Corrections for absorption, divergence and second order diffuse scattering were found negligible. The values of elastic constants in units of 10¹⁰ dynes.cm^-2 are: c₁₁ =41.0, c₂₂=5.2 c₃₃ =9.4, c₄₄=0.74 c₅₅ = 6.70 c₆₆=8.4 c₁₂=12.2 c₂₃=6.6 and c₁₃=14.6. The accuracy of the elastic constants is estimated to be within 15%.