Adsorption of CO over the Heusler alloy CrCoIrGa(001) surface: first-principles insights.

In this study, the adsorption of CO molecule over (001) surface of the Heusler alloy CrCoIrGa, has been investigated using DFT+U calculations. It is demonstrated that, after relaxation, the (001) surface retains the bulk atomic positions, exhibiting no apparent surface reconstruction. Owing to the emergence of unsaturated bonds at the surface, the surface layer atoms are found to carry more spin-polarization (SP) and atomic moments than that of inner layer atoms. The ground state total SP (magnetic moment) is found to be 27% (42.256 µ B). To explore the CO adsorption over the surface, five different adsorption configurations (sites) are considered and the strength of CO to surface interaction is estimated from the computed density of states (DOS), adsorption energy (E a), change in magnetic moment (ΔM), vertical height between molecule and surface (h), charge transfer (ΔQ), and charge density difference (CDD) plots. For all configurations, the E a lies in the range of -2.15 to -2.34 eV, with CO molecule adsorbed on the top of Ir atom as the most favorable adsorption configuration. The observed E a, ΔQ, h, and ΔM values, collectively predict that the (001) surface has strong interaction (chemisorption) with CO gas molecule, thus, might be useful in gas sensing applications.

Effect of Si, Be, Al, N and S dual doping on arsenene: first-principles insights.

First-principles calculations based on density functional theory (DFT) have been performed to investigate the effect of Si/Be, Si/Al, Si/N and Si/S co-doping on the geometries, electronic structure, magnetism and particularly the adsorption of CO in arsenene. The results show that the incorporation of foreign atoms slightly distorts the host lattice. All doped structures are found to be thermodynamically stable. The replacement of host As atoms with foreign atoms results in some interesting changes in the electronic and magnetic properties of arsenene. The doped arsenene systems exhibit a semiconducting character with band gaps smaller than the original value of 1.59 eV due to the emergence of defect states within the actual band gap. Besides, arsenene remains nonmagnetic (NM) upon Si/Be or Si/S dual doping, whereas both Si/Al and Si/N dopings induce magnetism with a total magnetic moment of 1 µB. Finally, the adsorption of CO molecules over pristine arsenene (p-As) and dual doped arsenene systems is investigated in terms of adsorption energy, adsorption height, charge transfer, charge density difference (CDD), work function, electronic band structures and density of states. It is observed that CO molecule has physisorption over p-As, SiAl-As, SiN-As and SiS-As systems, whereas chemisorption is reported for the SiBe-As system. Our study suggests that chemically modifying arsenene with suitable dopants might extend its applications in spintronic and gas sensing applications.