Theoretically proposed another stable polymorph of two-dimensional penta-PdPSe

Abstract

The theoretical discovery of new and stable 2D penta materials has stimulated the technological advancement due to the anticipated exotic properties of such structure, including the recent $\alpha$ phase and $\beta$ phase of penta-NiPS based on first-principles calculations. Inspired by the similarity between the theoretically proposed penta-NiPS and the experimentally synthesized ($\alpha$ phase) of penta-PdPSe, we preposed herein the $\beta$ phase penta-PdPSe as a new member of the penta-2D materials. Comprehensive analysis indicated that the $\beta$ phase penta-PdPSe is thermodynamically, dynamically, mechanically, and thermally stable, similar to the NiPS analog. It was found that $\beta$ penta-PdPSe is a wide band gap semiconductor with an indirect band gap of 1.58 eV, significantly lower than 2.15 eV for the $\alpha$ phase. Moreover, the two polymorphs of penta-PdPSe are a soft material with 2D Young's modulus of $E_a$ = 151 Nm$^-1$ and $E_b$ = 123 Nm$^-1$ for the $\beta$ phase, to be compared with $E_a$ = 155 Nm$^-1$ and $E_b$ = 113 Nm$^-1$ for the $\alpha$ phase. The calculated adsorption coefficient shows that $\beta$ phase penta-PdPSe is acceptable for electronic and optical nanodevice.