Density Functional Study of the Electronic, Photovoltaic, Elastic, and Infrared Properties of P‐62m Na X P ( X   = Sr, Ba)

Zintl compounds have many technological applications, although they are formed by electropositive and electronegative elements via a simple chemical bonding rule. Only a few of them crystallize in the ZrNiAl‐type structure. In this work, we selected P‐62m Na X P ( X  = Sr, Ba) as representative compounds to study their electronic, photovoltaic, elastic, and infrared properties using the density functional method. Calculated phonon spectra confirm their dynamical stability. Band structures and electron localization functions reveal both crystals to be narrow direct‐gap semiconductors with ionic bonding. The origins of the band structures are revealed by calculated partial densities of states and their respective spectroscopic limited maximum efficiencies are calculated. Obtained elastic constants uncover that these two crystals are mechanically stable but anisotropic. Investigations into the elastic‐related properties of P‐62m Na X P ( X  = Sr, Ba) unveil that both crystals are brittle, more resistant to volume change, and characterized by low hardness and low Debye temperature. Infrared spectra are simulated, and the vibrational modes at the Brillouin zone center are assigned by factor group analysis. In addition, their dielectric constants and piezoelectric coefficients are also computed and discussed.