First-principles studies of structural, electronic, and dynamical properties of Be chalcogenides

We have studied structural, electronic, and dynamical properties of Be chalcogenides (BeS, BeSe, and BeTe) by employing the plane-wave pseudopotential method within the density functional theory. The calculated lattice constant and bulk modulus for these compounds are found to be in good agreement with previous theoretical and experimental results. The electronic band structure is also presented for these materials. In particular, the calculated electronic valence band structure for BeTe shows very good agreement with an angle-resolved synchrotron-radiation photoemission spectroscopy data along the [100] direction. Phonon dispersion curves and density of states were calculated by employing a density-functional perturbation theory. It is found that the dispersion characteristics of the optical branches in these materials are very different from those of any other II-VI materials. An explanation of these characteristics is forwarded in terms of the large mass difference between Be and the chalcogens