Theoretically proposed stable polymorph of two-dimensional pentagonal β-PdPSe

The theoretical discovery of new and stable 2D penta materials based on first-principles calculations has stimulated technological advances due to the anticipated exotic properties of such structures, which include the α and β phases of penta-NiPS. Inspired by the similarity between the theoretically proposed penta-NiPS and the experimentally synthesized (α phase) of penta-PdPSe, we propose herein the β phase of penta-PdPSe as a new penta-2D material. Comprehensive analyses indicated that β phase penta-PdPSe is thermodynamically, dynamically, mechanically, and thermally stable, similar to its NiPS analogue. It was found that β 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 α phase. Moreover, the two polymorphs of penta-PdPSe are soft materials with 2D Young's modului of E_a = 151 N m^-1 and E_b = 123 N m^-1 for the β phase, compared with E_a = 155 N m^-1 and E_b = 113 N m^-1 for the α phase. The calculated absorption coefficient showed that β phase penta-PdPSe is acceptable for electronic and optical nanodevices.