Search for: All records

Abstract Here, we used a combination of laser‐induced experiments and density functional theory (DFT) calculations to study the mechanism of growth of carbonaceous species on the Mg surface. Experimental observations revealed that the carbon deposit forms upon laser illumination on the Mg surface, with the deposit being clearer and better structured in the presence of 1,3‐butadiene (C₄H₆) compared to ethylene (C₂H₄) gas. DFT thermodynamic and kinetic calculations of C₂−C₄hydrocarbons interaction on low‐index Mg(0001) were used to explain this experimental observation. Our results on Mg(0001) showed that the cis isomer of C₄H₆binds more strongly than its trans isomer via a [4+2] cycloaddition mechanism. We also investigated the adsorption of two units of C₂H₄and C₄H₆molecules, as well as the subsequent dehydrogenation stages that produce radical species responsible for chain growth mechanisms. The results showed that free energy change of dehydrogenation of two units of cis‐C₄H₆[i. e. cis‐C₈H₁₂] is lower than the dehydrogenation of trans conformer of C₄H₆and C₂H₄molecule, indicating that the dehydrogenation of two units of cis‐C₄H₆facilitates the initiation of growth of carbonaceous species on Mg surfaces. Therefore, the DFT calculations pinpoint the origin of the experimental observation of clearer carbon deposits on the Mg surface. 

Density functional theory (DFT) calculations are performed to compute the lattice constants, formation energies and vacancy formation energies of transition metal nitrides (TMNs) for transition metals (TM) ranging from 3d–5d series. The results obtained using six different DFT exchange and correlation potentials (LDA, AM05, BLYP, PBE, rPBE, and PBEsol) show that the experimental lattice constants are best predicted by rPBE, while the values obtained using AM05, PBE, rPBE and PBEsol lie between the LDA and BLYP calculated values. A linear relationship is observed between the lattice constants and formation energies with the mean radii of TM and the difference in the electronegativity of TM and N in TMNs, respectively. Our calculated vacancy formation energies, in general, show that N-vacancies are more favorable than TM-vacancies in most TMNs. We observe that N-vacancy formation energies are linearly correlated with the calculated bulk formation energies indicating that TMNs with large negative formation energies are less susceptible to the formation of N-vacancies. Thus, our results from this extensive DFT study not only provide a systematic comparison of various DFT functionals in calculating the properties of TMNs but also serve as reference data for the computation-driven experimental design of materials.