**1. Introduction**

Researchers have focused on II-VI semiconductors, which are intended for technological applications. BeSe crystallizes in zinc blend structure at room temperature and its properties depend on structure, pressure, temperature, and calculation method. The HSE hybrid underestimates the lattice parameters compared to GGA-PBE and LDA but gives a bandgap in accordance with the experimental value. The phonon dispersion curve of BeSe shows two optical and acoustic couplets and confirms its stability. The maximum of reflectivity (63% and 56%) is observed in the ultraviolet light domain. We expose the detailed calculation concerning the lattice parameters, elastic constants, bandgap, phonons frequencies, and optical parameters. For works carried out by other researchers, we note the transition from zinc blend phase to NiAs structure at 55 GPa [1]. The study of elastic constants and bandgap of BeSe in zinc blend phase [2, 3], the experimental bandgap ranging from 2 eV to 4.5 eV [4, 5], a small ionic radius ratio, a high degree of covalent bonding, and high hardness [6]. Appropriate bandgap and optical absorption parameters make BeSe as an important material in the area of catalysis and luminescent devices [7–9].
