Effect of Elastic Constants on the Ultrasonic Properties of Group VIB Transition Metal Diborides

Abstract

The ultrasonic properties like ultrasonic attenuation, sound velocity in the group VIB transition metal diborides like CrB2 and MoB2 have been studied along unique axis at room temperature. The second- and third order elastic constants (SOEC & TOEC) have been calculated for these diborides using Lennard- Jones potential. The velocities VL and VS2 increases with the angle from the unique axis and VS1 have maximum at 45 0 with unique axis of the crystal. The inconsistent behaviour of angle dependent velocities is associated to the action of second order elastic constants. Debye average sound velocities of these compounds are increasing with the angle and has maximum at 55 0 with unique axis at room temperature. Hence when a sound wave travels at 55 0 with unique axis of these materials, then the average sound velocity is found to be maximum. The mechanical properties of CrB2 are better than MoB2, because CrB2 has low ultrasonic attenuation comparison t h a n MoB2. The comparison of calculated ultrasonic parameters with available theoretical/experimental physical parameters gives information about classification of these compounds.