Abstract
The phonon dispersion curves for bulk metallic glasses (BMGs) Pd40Ni10Cu30P20 and Pd64Ni16P20 are computed for the longitudinal and transverse phonon frequencies using the simple model given by Bhatia and Singh. Different dielectric screening functions are employed for the longitudinal mode. We obtain the values of the force constants β and δ calculated from the elastic constants of the material of the respective BMGs for computing the dispersion curves. The computed phonon dispersion curves show appropriate behaviour for both the longitudinal and transverse modes. The transverse sound velocity and the longitudinal sound velocities with various dielectric screenings are calculated in the long wavelength region from the computed dispersion curves for both the BMGs. The first peak position of the static structure factor is predicted from the dispersion curves. The values of sound velocities and the first peak of the static structure factor estimated from the computed dispersion curves show excellent agreement with the experimental values reported in literature for the BMGs under consideration and the results may be used for correlating other properties of the BMGs.
Highlights
The phonon dispersion curves for bulk metallic glasses (BMGs) Pd40Ni10Cu30P20 and Pd64Ni16P20 are computed for the longitudinal and transverse phonon frequencies using the simple model given by Bhatia and Singh
To study its effect on the phonon frequencies, various dielectric screening functions [13] namely, Bhatia and Singh (BS), Hartree (H), Hubbard (HB), Geldart and Vosko (GV), self-consistent screening due to Shaw (SCS) and Overhauser (OH) are employed for the longitudinal mode
The phonon dispersion curves computed for the BMGs Pd40Ni10Cu30P20 and Pd64Ni16P20 using the simple model given by Bhatia and Singh [8] are shown in Figure 1a and 1b respectively
Summary
The phonon dispersion curves for bulk metallic glasses (BMGs) Pd40Ni10Cu30P20 and Pd64Ni16P20 are computed for the longitudinal and transverse phonon frequencies using the simple model given by Bhatia and Singh. In the approach adopted by us, we fix the values of force constants δ and β used in the computation of dispersion curves by using the value of bulk modulus (B) and shear modulus (G) of the respective BMGs along with the calculated value of κe This method of determining the values of δ and β from the elastic modulii of the BMGS for computing phonon frequencies using the simple model is applied for the first time for the Pd40Ni10Cu30P20 and Pd64Ni16P20 BMGs. The dielectric screening due to conduction electrons in the long wavelength region of the phonon frequencies is quite significant. In equations (1) and (2), I can be written as [8]
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