A comparative evaluation of elasticity in pentaerythritol tetranitrate using Brillouin scattering and resonant ultrasound spectroscopy

Elastic tensors for organic molecular crystals vary significantly among different measurements. To understand better the origin of these differences, Brillouin scattering and resonant ultrasound spectroscopy measurements were made on the same specimen for single crystal pentaerythritol tetranitrate. The results differ significantly despite mitigation of sample-dependent contributions to errors. The frequency dependence and vibrational modes probed for both measurements are discussed in relation to the observed tensor variance.