A first-principles investigation of structural, thermodynamic, electronic, and optical properties of doped 2D ZrNI monolayer

The density functional theory has been used to investigate the structural, thermodynamic, electronic, and optical properties of two-dimensional (2D) ZrNI monolayers without and with doped states formed by P, Cl and Br. All three acoustic and optical modes have non-zero frequencies, demonstrating the stability of the ZrNI monolayer. The separated optical and acoustic modes at lower frequencies are proportional to the crystal momentum, representing that the phase velocity of the monolayer is nearly constant in wavelength. The thermodynamically stable 2D ZrNI monolayer has a comparatively low heat capacity and moderate Deby temperature. The 2D ZrNI monolayer is an indirect bandgap semiconductor with a gap width of 0.80 eV. Halogen (Cl and Br) doping increases the gap width to 0.85 and 0.84 eV, while P doping reduces the bandgap to 0.67 eV. Upon doping, all the materials maintained the indirect nature of the band diagram. The total density of states of the pristine and doped 2D ZrNI monolayer exposed contemptible electronic accessibility at the Fermi level, thereby envisaging the semi-metallic nature of the monolayer. The band structure analysis indicated the non-dispersive behaviour of the monolayer in the first Brillouin zone (BZ) and the dispersive nature in the k -space through the energy range from -2.00 eV to 3.00 eV. Pristine ZrNI monolayer absorbs light up to the mid-visible spectrum, and Br and P doping raise the absorption capability to the entire visible range with sharp peaks at the UV range.