In this paper, we present a detailed investigation of the structural, electronic, and optical properties of pristine, nitrogenated, and fluorinated MgO monolayers using ab initio calculations. The two dimensional (2D) material stability is confirmed by the phonon dispersion curves and binding energies. Full functionalization causes notable changes in the monolayer structure and slightly reduces the chemical stability. The simulations predict that the MgO single layer is an indirect semiconductor with an energy gap of 3.481 (4.693) eV as determined by the GGA-PBE (HSE06) functional. The electronic structure of the MgO monolayer exhibits high sensitivity to chemical functionalization. Specifically, nitrogenation induces metallization of the MgO monolayer, while an indirect–direct band gap transition and band gap reduction of 81.34 (59.96)% are achieved by means of fluorination. Consequently, the functionalized single layers display strong optical absorption in the infrared and visible regimes. The results suggest that full nitrogenation and fluorination may be a quite effective approach to enhance the optoelectronic properties of the MgO monolayer for application in nano-devices.

General one-loop contributions to the decay processes $$H\rightarrow f\bar{f}\gamma $$H → f f ¯ γ and its applications are presented in this paper. We consider all possible contributions of the additional heavy vector gauge bosons, heavy fermions, and charged (also neutral) scalar particles propagating in Feynman loop diagrams. Therefore, analytic results are valid in a wide class of models beyond the Standard Model. Analytic formulas for the form factors are expressed in terms of Passarino-Veltman functions in the standard notations of . Hence, the decay rates can be evaluated numerically by using this package. The computations are then applied to the cases of the Standard Model, $$U(1)_{B-L}$$U ( 1 ) B - L extension of the Standard Model as well as Two Higgs Doublet Model. Phenomenological results for all the above models are studied. We observe that the effects of new physics are sizable contributions and these can be probed at future colliders.

Designing new two-dimensional (2D) materials based on the Janus structure has attracted great attention due to their novel properties induced by out-of-plane symmetry breaking. In this work, we have systematically investigated the structural and electronic properties of TMSeO (TM = Mo and W) monolayers, which can be obtained by oxygenation of the TMSe₂ counterpart. Phonon dispersion curves confirm good dynamical stability. MoSeO and WSeO pristine monolayers are Γ–K indirect gap semiconductors with energy gaps of 0.815(1.324) and 1.323(1.894) eV as determined using the PBE(HSE06) functional, respectively. Our calculations show that a single vacancy of each constituent atoms leads to magnetism-free 2D materials, although it induces a considerable energy-gap reduction. A small lattice constant mismatch between the MoSeO and WSeO monolayers allows the formation of heterostructures. Depending on the stacking, vertical heterostructures (VHSs) exhibit different electronic features, including being a semiconductor with a variable band gap, a semimetal, and metallic in nature. Meanwhile, in lateral heterostructures (LHSs) the semiconductor behavior remains, for which the band gap increases according to an increase in the WSeO block composition. This work provides a deeper insight into the TMSeO monolayers as well as their effective gap engineering based on the formation of defects and heterostructures. The obtained results may introduce new 2D materials, which have the potential for applications in high-performance optoelectronic nano devices.

In this work, defect engineering and doping are proposed to effectively functionalize a germanium sulfide (GeS) mononolayer. With a buckled hexagonal structure, the good dynamical and thermal stability of the GeS monolayer is confirmed. PBE(HSE06)-based calculations assert the indirect gap semiconductor nature of this two-dimensional (2D) material with a relatively large band gap of 2.48(3.28) eV. The creation of a single Ge vacancy magnetizes the monolayer with a total magnetic moment of 1.99 μ_B, creating a the feature-rich half-metallic nature. Va_S vacancy, Va_GeS divacancy, S_Ge and Ge_S antisites preserve the non-magnetic nature; however, they induce considerable band gap reduction of the order 47.98%, 89.11%, 29.84%, and 62.5%, respectively. By doping with transition metals (TMs), large total magnetic moments of 3.00, 4.00, and 5.00 μ_B are obtained with V, Cr–Fe, and Mn impurities, respectively. The 3d orbital of TM dopants mainly regulates the electronic and magnetic properties, which induces either the half-metallic or diluted magnetic semiconductor nature. It is found that the doping site plays a determinant role in the case of doping with VA-group atoms (P and As). The GeS monolayer can be metallized by doping the Ge sublattice, meanwhile both spin states exhibit semiconductor character with strong spin polarization upon doping the S sublattice to obtain a diluted magnetic semiconductor nature with a total magnetic moment of 1.00 μ_B. In these cases, the magnetism originates mainly from P and As impurities. The obtained results suggest an efficient approach to functionalize the GeS monolayer for optoelectronic and spintronic applications.

Defect engineering and doping are proposed as efficient approaches to create new 2D multifunctional materials from a non-magnetic semiconductor PdO₂ monolayer.

Based on the density functional theory in combination with the nonequilibrium Green’s function formalism, we study the structural, electronic, and transport properties of SS-pSiC₂ NRs under a sequence of uniaxial strains in the range from 10% compression to 10% stretch. The pentagon network of SS-pSiC₂ NRs is still maintained, but the bond length along the strained direction is largely changed under this strain. The electronic band structure and bandgap are strongly affected by the uniaxial compressive strain. The evolution of the bandgap vs the strain is linear. With a bias voltage of 2 V, the current of the 10% compressed sample increased 75 times, and the current of the 10% stretched sample increased 2.5 times compared to the one of the relaxed sample. The I–V characteristic of SS-pSiC₂ NRs seems to be more sensitive to compressive strain than the stretch strain. Our calculations may indicate new applications of strain structures in electromechanical devices based on SS-pSiC₂ NRs.