LAUSR

Abstract Higher order elastic constants have been calculated in semi-metallic superconducting single crystal magnesium diboride (MgB2) at low temperatures following the interaction potential model. Second order elastic constants are used for the determination of other ultrasonic parameters. The pressure variation of the ultrasonic velocities is evaluated using the second order elastic constants. The ultrasonic attenuation due to electron-phonon interaction has been computed at different pressures and in low temperatures range 40–90 K. We have also calculated the electron-viscosity at different low temperature, needed for the calculation of ultrasonic attenuation. The behaviour of ultrasonic attenuation is almost similar to its inverse electrical resistivity. The electron–phonon interaction, which is the dominating cause of ultrasonic attenuation, occurs at lower temperatures in MgB2 single crystal. It has been found that the electrical resistivity is the main contributor to the behaviour of ultrasonic attenuation as a function of temperature and the responsible cause of attenuation is phonon-phonon interaction.