Search

The geometric and electronic structures of the ethylene oxide (EO) molecule adsorbed on Si(100)- surface were investigated by using the density-functional theory calculations. All possible adsorbed structures were considered and it was found that only four adsorption structures are stable. The calculations of the formation energy revealed the most stable conformation and demonstrated that the nature of Si-O bond significantly affects the stability of adsorption systems. The analysis of corresponding electronic structures showed that two adsorbed structures are still semiconductor compounds but the other two are not. In particular, the EO after adsorbing was found to be connected via a ring-opening reaction where the molecule forms a five-membered ring together with the surface of dimer silicon atoms, and the produced five-membered ring is almost perpendicular to the silicon surface. [ABSTRACT FROM AUTHOR]

Abstract: The structural, magnetic and electronic properties of Co2MnGe0.75Ga0.25 have been studied by first-principles calculations. Co2MnGe0.75Ga0.25 is found to be nearly half-metallic. The calculated lattice constant and magnetic moments are found to be in good agreement with experiments. Furthermore, we investigate the effect of pressure on the electronic structure and magnetic properties of Co2MnGe0.75Ga0.25. The calculated results show a nearly half-metallic to half-metallic (HM) transition at 12GPa. Then the half-metal to metal transition is observed at 97GPa. The calculations show that pressure mainly affects the minority spin states, leading to a slight reconstruction of the minority spin bands with a shift in the Fermi level driving the above-mentioned transition. [Copyright &y& Elsevier]

Abstract: The electronic structure and magnetic properties of Co-doped Heusler alloys VGa (x=0.0, 0.25, 0.5, 0.75, 1.0) have been studied by first-principles calculations. The results show that the lattice constants decrease with increasing Co content except x=1.0. The spin polarization for x=0.5 is only 34%, much lower than the other concentrations. The compounds of x=0.0, 0.25 show nearly half-metallicity because the Fermi level slightly touches the valence bands. And the compounds of x=0.75, 1.0 exhibit the half-metallic character with 100% spin polarization. It is found the local moments of Mn(Co) basically show a linear increasing trend while the moments of V show a linear decreasing trend with increasing doping concentration. However, the local moments for x=0.5 quite depart from the linear trend. The majority-spin component at the Fermi level increases while the minority-spin component at the Fermi level decreases with the substitution of Co atoms for Mn atoms when . For , the majority-spin component remains more or less the same and the gap in the minority DOS increases with Co doping. The majority spin states are shifted to valence bands and the majority spin states around E F increase due to a leakage of charge from the unoccupied spin-up states to the occupied majority states with increasing Co content. [Copyright &y& Elsevier]

Abstract: We have investigated the electronic and magnetic properties of the doped Heusler alloys Co2Fe1−xV xAl (, 0.25, 0.5, 0.75, 1) using first-principles density functional theory within the generalized gradient approximation (GGA) scheme. The calculated results reveal that with increasing V content the lattice parameter slightly increases. The magnetic moment of the Fe sites increases while the magnetic moment of the Co sites decreases with V doping; the total spin moment of these compounds linearly decreases. We also have performed the electronic structure calculations for Co2Fe1−xV xAl with positional disorder of Co–Fe(V) type and Al–Fe(V) type. It is found that formation of Al–Fe(V)-type disorder is more favorable than that of Co–Fe(V)-type disorder in Co2Fe1−xV xAl alloys. Furthermore, we found that the spin polarization increases with V doping in Co2Fe1−xV xAl with ordered and disordered B2 structures. Detailed calculations show that the stability of the structure will be enhanced with increasing V content. The results are compatible with experiments. [Copyright &y& Elsevier]