Zur Temperaturabhängigkeit der elastischen Konstanten von Alkalihalogenidkristallen

Calculations were made to investigate the anharmonic properties of lead chalcogenides PbS, PbSe and PbTe at elevated temperatures by means of primary physical parameters viz. nearest-neighbour distance and hardness parameter using long-and short-range potentials. Higher-order elastic constants are computed up to their melting temperature for these crystals. The first order pressure derivatives of second-and third-order elastic constants, the second-order pressure derivatives of second-order elastic constants and partial contractions are also evaluated at different temperatures. As the experimental elastic constants are not available at high temperatures, hence our results were only compared with the available values obtained at room temperature. The nature of the elastic behaviour in these compounds was analyzed.

Section: Discussionmentioning

confidence: 99%

Section: Theorymentioning

confidence: 99%

Temperature Dependent Anharmonic Properties of Lead Chalcogenides

Raju

2010

“…Second-and third-order elastic moduli at temperature, T are the sum of elastic moduli at absolute zero temperature and vibrational contribution to second-and third-order elastic moduli at corresponding temperature [19][20][21][22] …”

Section: Elastic Modulimentioning

confidence: 99%

Effect of Temperature on Non-Destructive Wave Propagation in Uranium Monopnictides

Singh

Chaurasia

2009

Acoustic attenuation due to phonon-phonon interaction, thermoelastic mechanism and dislocation damping were evaluated in uranium monopnictides (viz. UN, UAs and USb) in the temperature range 50-500 K, along the three crystallographic directions of propagation, viz.[100], [110] and [111] for longitudinal and shear modes of propagation. Due to antiferromagnetic property of these compounds ultrasonic attenuation due to magnon-phonon interaction was also obtained. The second-and third-order elastic moduli of B1-type uranium monopnictides were obtained using electrostatic and the Born repulsive potentials. Gruneisen numbers and acoustic coupling constants were evaluated for longitudinal and shear waves along different directions of propagation and polarization. Results were discussed and compared with available data. It was found that the temperature dependence of attenuation due to phonon-phonon interaction and thermoelastic loss mechanisms follow the third and fourth order polynomial fit laws, respectively, and acoustic attenuation is mainly governed by phonon-phonon interaction in this temperature range.

“…The elastic constants of the second, third and fourth order are defined as [24] The free energy density [25,26] of a crystal at a flnite temperature Τ is where U0 is the inteual energy per unit volume of the crystal when all ions are at rest on their lattice points, Uvib is the vibrational free energy, Vc is the volume of the primitive cell, N is the number of the primitive cells in the crystal and s is the number of ions in the elementary cell. Other notations used in this equations have their usual meanings.…”

Section: Formulationmentioning

confidence: 99%

Anharmonic Properties of Alkali Halides and Cyanides

Kailash

1996

Anharmonic properties of 16 alkali halides and 4 alkali cyanides are investigated using long-range Coulomb and short-range Born-Mayer potentials starting from the nearest-neighbour distance and repulsive parameter. This study includes the prediction of second, third and fourth order elastic constants, the pressure derivatives of second and third order elastic constants and partial contractions at elevated temperatures. The results obtained in present investigations are in reasonable agreement compared with experimental studies.