Theoretical prediction of alkali oxide M2O (M = Na and K) monolayers and formation of their Janus structure. (30th August 2022)

• Record Type: Journal Article
• Authors: Lien, Vu Thi Kim; Van On, Vo; Guerrero-Sanchez, J.; Rivas-Silva, J. F.; Cocoletzi, Gregorio H.; Hoat, D. M.
• Is Part Of: New journal of chemistry. Volume 46:Number 36(2022)
• Page Start: 17386
• Page End: 17393
• Publication Date: 2022-08-30
• Subjects: Chemistry -- Periodicals; Chimie -- Périodiques; 540
• DOI: 10.1039/d2nj03118c
• Languages: English
• ISSNs: 1144-0546

Abstract

Abstract : Formation of the Janus structure. Abstract : In this work, a first-principles study of Na2 O and K2 O monolayers and their Janus structure has been carried out using density functional theory calculations based on the projector-augmented plane wave method. Good structural stability is confirmed by phonon dispersion curves and formation enthalpy. The formation of the NaKO monolayer starting from either Na2 O or K2 O is analyzed via the surface formation energy method. The experimental feasibility with the exothermic synthesis process is demonstrated, mostly in Na-poor or K-poor conditions. Na2 O and NaKO monolayers are direct gap semiconductors with band gaps of 0.97 (1.97) and 0.51 (1.21) eV, respectively, as calculated using the PBE (HSE06) functional. Meanwhile, the K2 O monolayer exhibits an indirect gap semiconductor character with an energy gap of 0.52 (1.28) eV. The ionic nature is also confirmed by means of the projected density of states and charge density difference. In addition, the 2D materials studied herein exhibit good absorption in a wide energy range from the visible to ultraviolet region with large absorption coefficients of the order of 10 5 (cm −1 ), indicating their potential to be applied in optoelectronic devices.