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[Display omitted] • Novel Janus Monolayer 1T'-MoSF is found through theoretical calculations. • Janus Monolayer 1T'-MoSF has high energetic, mechanical, dynamical, and thermodynamic stability. • Janus Monolayer 1T'-MoSF exhibits significant anisotropy, and superior mechanical flexibility. Janus monolayers of transition-metal dichalcogenides (TMDs) have garnered significant attention in various scientific fields due to their exceptional physical properties. Among the known Janus monolayer TMDs, MoSX holds particular significance, with X typically representing chalcogen atoms. The successful synthesis of MoSH has pushed the boundaries of X beyond the conventional chalcogens. Nevertheless, it remains an open question whether other elements can also yield stable Janus monolayer MoSX. Herein, we employ theoretical methods to undertake a comprehensive evaluation of the stability of Janus monolayer MoSX (X = Li, Be, B, C, N, F, Na, Mg, Al, Si, P, Cl). The analysis of stability encompasses various aspects, including energetic, mechanical, dynamical, and thermodynamic features. Interestingly, our investigations have revealed the existence of a hitherto undiscovered stable 1T'-MoSF structure. Remarkably, this structure exhibits significant anisotropy, providing superior mechanical flexibility due to its low Young's modulus. In addition, despite the dynamical instability of 2H/1T-MoSN and the mechanical instability of 2H/1T-MoSC/Mg, they could potentially exist under specific conditions. This theoretical study not only provides insights into the structural characteristics and stability of novel Janus monolayer MoSX, but also extends the Janus monolayer MoSX family, which would be valuable to future applications of Janus TMDs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Iodine vacancy did not create midgap states in CsPbI 3 perovskites. • The carriers separation was governed by both surface defects and dipolar stabilizer. • The excited dynamics of electron relaxation was explored. • We explained the mechanism of dipolar passivator regulating carriers lifetime. The surface properties including both defect-modified and surface functionalization by dipolar molecules has a significant influence on the dynamics of charge carriers within metal halide perovskites (MHPs), which is crucial for achieving highly efficient and stable optoelectronic devices. Herein, we considered the sulfobetaine (SFB) as a model structure of dipolar molecular stabilizer, and systematically explored the surface defects and SFB passivation to regulate geometrical/electronic structures of perovskites, as well as its impact on spatial separation of photogenerated carriers by first-principles calculations. We further utilized time-dependent ab initio nonadiabatic molecular dynamics to simulate the photogenerated carrier dynamical behavior and elucidate the exact influence of surface iodine vacancy and SFB passivators have in tuning excited state lifetime. These theoretical results provide insight into physical mechanism behind defect passivation via dipolar stabilizers, promising routes towards improved optoelectronic applications for MHPs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Rutile MnO 2-δ film is used to demonstrate the regulation of the orbital occupation. • Orbital polarization change in MnO 2-δ films is obtained by reductvie annealing. • Significant enhanced magnetic moments in MnO 2-δ films can be detected below 50 K. Effectively manipulating the orbital configuration is an emerging method to design quantum functional materials with novel electronic ground states. Here, we report the realization of orbital polarization change in rutile MnO 2-δ epitaxial thin films by reductive treatments such as CaH 2 coating annealing and hydrogen atmosphere annealing. These treated samples show significant lattice expansion due to the generation of oxygen vacancies and incorporation of H, and the mixed valence states of Mn2+ and Mn3+ are formed with the decrease in the Mn valence state. The X-ray linear dichroism results show that the electron occupied state of Mn in the treated film samples changes from 3d 3z 2 -r 2 to 3d x 2 -y 2, which means that the deprivation of oxygen atoms in the oxygen octahedron of MnO 6 causes a change of orbital polarization. The resulting high spin state in the treated MnO 2-δ films greatly enhances the magnetic properties of the films. This work not only demonstrates how the oxygen atoms in the edge-shared oxygen octahedron of rutile structures are replaced by reduction but also extends the study of orbital polarization and magnetic ground state control in oxide epitaxial films. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pristine C 3 N monolayer shows stronger O 2 physisorption than pristine graphene. • The most preferable O 2 dissociation is an indirect two-step path with chemisorbed O 2. • Two dangling C-O bonds on the para-carbon site is the most stable oxidized structure. • Pristine C 3 N monolayer is more susceptible to oxidation than pristine graphene. • Electronic properties can be altered significantly due to the presence of two chemisorbed O atoms. The oxygen dissociation and the oxidized structure on the pristine C 3 N monolayer in exposure to air are the inevitably critical issues for the C 3 N engineering and surface functionalization yet have not been revealed in detail. Using the first-principles calculations, we have systematically investigated the possible O 2 adsorption sites, various O 2 dissociation pathways and the oxidized structures. It is demonstrated that the pristine C 3 N monolayer shows more O 2 physisorption sites and exhibits stronger O 2 adsorption than the pristine graphene. Among various dissociation pathways, the most preferable one is a two-step process involving an intermediate state with the chemisorbed O 2 and the barrier is lower than that on the pristine graphene, indicating that the pristine C 3 N monolayer is more susceptible to oxidation than the pristine graphene. Furthermore, we found that the most stable oxidized structure is not produced by the most preferable dissociation pathway but generated from a direct dissociation process. These results can be generalized into a wide range of temperatures and pressures using ab initio atomistic thermodynamics. Our findings deepen the understanding of the chemical stability of 2D crystalline carbon nitrides under ambient conditions, and could provide insights into the tailoring of the surface chemical structures via doping and oxidation. [ABSTRACT FROM AUTHOR]