The interfaces in 2D hybrids of graphene and h-BN provide interesting possibilities of adsorbing ... more The interfaces in 2D hybrids of graphene and h-BN provide interesting possibilities of adsorbing and manipulating atomic and molecular entities.
In this communication we have studied the electronic structure, magnetic and optical properties o... more In this communication we have studied the electronic structure, magnetic and optical properties of bcc \fecr alloys in the ferromagnetic phase. We have used the augmented space recursion technique coupled with tight-binding linearized muffin-tin orbital technique (TB-LMTO-ASR) as well as the coherent-potential approximation based on the Korringa-Kohn-Rostocker method (KKR-CPA). Also the plane wave projector augmented wave (PAW) method has been used with the disorder simulated by the special quasi-random structure method f or configuration averaging (SQS). This was to provide a comparison between the different methods in common use for random alloys. Moreover, using the self-consistent potential parameters from TB-LMTO-ASR ca lculations we obtained the spin resolved optical conductivity using the generalized recursion technique proposed by Müller and Vishwanathan.
We have calculated from first principles the electronic structure of 0.5 monolayer upto 5 monolay... more We have calculated from first principles the electronic structure of 0.5 monolayer upto 5 monolayer thick Fe layers on top of a GaAs (100) surface. We find the Fe magnetic moment to be determined by the Fe-As distance. As segregates to the top of the Fe film, whereas Ga most likely is found within the Fe film. Moreover, we find an asymmetric in-plane contraction of our unit-cell along with an expansion perpendicular to the surface. We predict the number of Fe 3d-holes to increase with increasing Fe thickness on p-doped GaAs.
In this paper, we have studied Te antisites and Cd vacancies in CdTe by local density approximati... more In this paper, we have studied Te antisites and Cd vacancies in CdTe by local density approximation (LDA) and hybrid functionals (HSE06) within density functional theory. We have shown that LDA, in ...
From data collected around the Z 0 resonance by the OPAL detector at LEP, a sample of B s decays ... more From data collected around the Z 0 resonance by the OPAL detector at LEP, a sample of B s decays was obtained using D − s ℓ + combinations, where the D − s was fully reconstructed in the φπ − , K * 0 K − and K 0 s K − decay channels or partially reconstructed in the φℓ −ν (X) decay channel. These events were used to study B s oscillation. The flavor (b orb) at decay was determined from the lepton charge while the flavor at production was determined from a combination of techniques. The expected sensitivity of the experiment is 4.1 ps −1. The experiment was not able to resolve the oscillatory behavior, and we deduced that the B s oscillation frequency ∆m s > 1.0 ps −1 at the 95% confidence level.
The binding affinity of explosive molecules with 2D BN flakes is higher than G flakes due to more... more The binding affinity of explosive molecules with 2D BN flakes is higher than G flakes due to more charge transfer in the BN-explosive complexes.
We present a method of extracting the exchange parameters of the classical Heisenberg model from ... more We present a method of extracting the exchange parameters of the classical Heisenberg model from first-principles calculations of spin-spiral total energies based on density functional theory. The exchange parameters of the transition-metal monoxides MnO and NiO are calculated and used to estimate magnetic properties such as transition temperatures and magnon energies. Furthermore we show how to relate the magnon energies directly to differences in spin-spiral total energies for systems containing an arbitrary number of magnetic sublattices. This provides a comparison between magnon energies using a finite number of exchange parameters and the infinite limit.
To shed light on the metal 3d electronic structure of manganese phthalocyanine, so far controvers... more To shed light on the metal 3d electronic structure of manganese phthalocyanine, so far controversial, we performed photoelectron measurements both in the gas phase and as thin film. With the purpose of explaining the experimental results, three different electronic configurations close in energy to one another were studied by means of density functional theory. The comparison between the calculated valence band density of states and the measured spectra revealed that in the gas phase the molecules exhibit a mixed electronic configuration, while in the thin film, manganese phthalocyanine finds itself in the theoretically computed ground state, namely, the b 1 e 3 a 1 b 0 electronic configuration.
The spin and orbital moments of Au/Co/Au trilayers grown on a W(110) single crystal substrate hav... more The spin and orbital moments of Au/Co/Au trilayers grown on a W(110) single crystal substrate have been investigated by means of x-ray magnetic circular dichroism. Our findings suggest that the orbital moment of Co does not obtain a maximum value along the easy axis, in contrast with previous experience. This is attributed to the large spin-orbit interaction within the Au caps. Both second order perturbation theory and first principles calculations show how the magnetocrystalline anisotropy (MCA) is dramatically influenced by this effect, and how this leads to the fact that the orbital moment anisotropy is not proportional to the MCA.
We have studied the atomic scale structure of molecular beam epitaxy grown Ga1-xMnxAs compounds w... more We have studied the atomic scale structure of molecular beam epitaxy grown Ga1-xMnxAs compounds with various Mn concentrations by cross-sectional scanning tunneling microscopy and first principles calculations. Only bright protrusions close to the top layer As atoms are directly correlated with the bulk Mn concentration. Atomically resolved filled and empty states images of this defect are compared to images derived
ABSTRACT The adsorption of FePc on Co(001) and c(2×2)O/Co(001) was studied by means of density fu... more ABSTRACT The adsorption of FePc on Co(001) and c(2×2)O/Co(001) was studied by means of density functional theory calculations, taking into account the long range van der Waals dispersion forces. Several high symmetry adsorption sites were analyzed, together with two possible orientations of the molecules. For the adsorption of FePc on the bare surface the on-top-of Co position, rotated by 45∘ relative to the substrate orientation, is most stable, whereas on the surface covered by an O adlayer the on-top-of O position is preferred. This has strong impact on the magnetic coupling but leaves the spin state of S =1 unaltered. The total energies of the studied adsorption sites on the bare metal differ by at least 0.75 eV and are characterized by a strong hybridization of the carbon atoms in the peripheral benzenic rings with the Co atoms beneath. In the presence of the O adlayer the various sites are closer in energy, which turns out to be related to the screening of the ferromagnetic film by the oxygen atoms.
We propose and briefly describe the generalized recursion in augmented space using a minimal TB-L... more We propose and briefly describe the generalized recursion in augmented space using a minimal TB-LMTO basis set for the calculation of configuration averaged current response functions in disordered binary alloys. Since disorder in the current terms is off-diagonal and non-separable, single-site mean-field approaches are unable to deal with it without further approximations. The augmented space approach is ideally suited for
We have studied the electronic structure of Co doped ZnO by theory and experiment. Photoelectron ... more We have studied the electronic structure of Co doped ZnO by theory and experiment. Photoelectron and x-ray absorption spectroscopy experiments were performed on 5% Co doped ZnO thin films. The results show that Co-3d states lie in the valence band and hybridize considerably with O-2p states. These results compare qualitatively with our density functional calculations combined with a Hubbard approach
The interfaces in 2D hybrids of graphene and h-BN provide interesting possibilities of adsorbing ... more The interfaces in 2D hybrids of graphene and h-BN provide interesting possibilities of adsorbing and manipulating atomic and molecular entities.
In this communication we have studied the electronic structure, magnetic and optical properties o... more In this communication we have studied the electronic structure, magnetic and optical properties of bcc \fecr alloys in the ferromagnetic phase. We have used the augmented space recursion technique coupled with tight-binding linearized muffin-tin orbital technique (TB-LMTO-ASR) as well as the coherent-potential approximation based on the Korringa-Kohn-Rostocker method (KKR-CPA). Also the plane wave projector augmented wave (PAW) method has been used with the disorder simulated by the special quasi-random structure method f or configuration averaging (SQS). This was to provide a comparison between the different methods in common use for random alloys. Moreover, using the self-consistent potential parameters from TB-LMTO-ASR ca lculations we obtained the spin resolved optical conductivity using the generalized recursion technique proposed by Müller and Vishwanathan.
We have calculated from first principles the electronic structure of 0.5 monolayer upto 5 monolay... more We have calculated from first principles the electronic structure of 0.5 monolayer upto 5 monolayer thick Fe layers on top of a GaAs (100) surface. We find the Fe magnetic moment to be determined by the Fe-As distance. As segregates to the top of the Fe film, whereas Ga most likely is found within the Fe film. Moreover, we find an asymmetric in-plane contraction of our unit-cell along with an expansion perpendicular to the surface. We predict the number of Fe 3d-holes to increase with increasing Fe thickness on p-doped GaAs.
In this paper, we have studied Te antisites and Cd vacancies in CdTe by local density approximati... more In this paper, we have studied Te antisites and Cd vacancies in CdTe by local density approximation (LDA) and hybrid functionals (HSE06) within density functional theory. We have shown that LDA, in ...
From data collected around the Z 0 resonance by the OPAL detector at LEP, a sample of B s decays ... more From data collected around the Z 0 resonance by the OPAL detector at LEP, a sample of B s decays was obtained using D − s ℓ + combinations, where the D − s was fully reconstructed in the φπ − , K * 0 K − and K 0 s K − decay channels or partially reconstructed in the φℓ −ν (X) decay channel. These events were used to study B s oscillation. The flavor (b orb) at decay was determined from the lepton charge while the flavor at production was determined from a combination of techniques. The expected sensitivity of the experiment is 4.1 ps −1. The experiment was not able to resolve the oscillatory behavior, and we deduced that the B s oscillation frequency ∆m s > 1.0 ps −1 at the 95% confidence level.
The binding affinity of explosive molecules with 2D BN flakes is higher than G flakes due to more... more The binding affinity of explosive molecules with 2D BN flakes is higher than G flakes due to more charge transfer in the BN-explosive complexes.
We present a method of extracting the exchange parameters of the classical Heisenberg model from ... more We present a method of extracting the exchange parameters of the classical Heisenberg model from first-principles calculations of spin-spiral total energies based on density functional theory. The exchange parameters of the transition-metal monoxides MnO and NiO are calculated and used to estimate magnetic properties such as transition temperatures and magnon energies. Furthermore we show how to relate the magnon energies directly to differences in spin-spiral total energies for systems containing an arbitrary number of magnetic sublattices. This provides a comparison between magnon energies using a finite number of exchange parameters and the infinite limit.
To shed light on the metal 3d electronic structure of manganese phthalocyanine, so far controvers... more To shed light on the metal 3d electronic structure of manganese phthalocyanine, so far controversial, we performed photoelectron measurements both in the gas phase and as thin film. With the purpose of explaining the experimental results, three different electronic configurations close in energy to one another were studied by means of density functional theory. The comparison between the calculated valence band density of states and the measured spectra revealed that in the gas phase the molecules exhibit a mixed electronic configuration, while in the thin film, manganese phthalocyanine finds itself in the theoretically computed ground state, namely, the b 1 e 3 a 1 b 0 electronic configuration.
The spin and orbital moments of Au/Co/Au trilayers grown on a W(110) single crystal substrate hav... more The spin and orbital moments of Au/Co/Au trilayers grown on a W(110) single crystal substrate have been investigated by means of x-ray magnetic circular dichroism. Our findings suggest that the orbital moment of Co does not obtain a maximum value along the easy axis, in contrast with previous experience. This is attributed to the large spin-orbit interaction within the Au caps. Both second order perturbation theory and first principles calculations show how the magnetocrystalline anisotropy (MCA) is dramatically influenced by this effect, and how this leads to the fact that the orbital moment anisotropy is not proportional to the MCA.
We have studied the atomic scale structure of molecular beam epitaxy grown Ga1-xMnxAs compounds w... more We have studied the atomic scale structure of molecular beam epitaxy grown Ga1-xMnxAs compounds with various Mn concentrations by cross-sectional scanning tunneling microscopy and first principles calculations. Only bright protrusions close to the top layer As atoms are directly correlated with the bulk Mn concentration. Atomically resolved filled and empty states images of this defect are compared to images derived
ABSTRACT The adsorption of FePc on Co(001) and c(2×2)O/Co(001) was studied by means of density fu... more ABSTRACT The adsorption of FePc on Co(001) and c(2×2)O/Co(001) was studied by means of density functional theory calculations, taking into account the long range van der Waals dispersion forces. Several high symmetry adsorption sites were analyzed, together with two possible orientations of the molecules. For the adsorption of FePc on the bare surface the on-top-of Co position, rotated by 45∘ relative to the substrate orientation, is most stable, whereas on the surface covered by an O adlayer the on-top-of O position is preferred. This has strong impact on the magnetic coupling but leaves the spin state of S =1 unaltered. The total energies of the studied adsorption sites on the bare metal differ by at least 0.75 eV and are characterized by a strong hybridization of the carbon atoms in the peripheral benzenic rings with the Co atoms beneath. In the presence of the O adlayer the various sites are closer in energy, which turns out to be related to the screening of the ferromagnetic film by the oxygen atoms.
We propose and briefly describe the generalized recursion in augmented space using a minimal TB-L... more We propose and briefly describe the generalized recursion in augmented space using a minimal TB-LMTO basis set for the calculation of configuration averaged current response functions in disordered binary alloys. Since disorder in the current terms is off-diagonal and non-separable, single-site mean-field approaches are unable to deal with it without further approximations. The augmented space approach is ideally suited for
We have studied the electronic structure of Co doped ZnO by theory and experiment. Photoelectron ... more We have studied the electronic structure of Co doped ZnO by theory and experiment. Photoelectron and x-ray absorption spectroscopy experiments were performed on 5% Co doped ZnO thin films. The results show that Co-3d states lie in the valence band and hybridize considerably with O-2p states. These results compare qualitatively with our density functional calculations combined with a Hubbard approach
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