M. Trioni - Academia.edu (original) (raw)
Papers by M. Trioni
Physical Review B, 2002
ABSTRACT By using a jellium model surface and a realistic one, the magnetic properties of a singl... more ABSTRACT By using a jellium model surface and a realistic one, the magnetic properties of a single Fe adatom on Al are studied. For the jellium surface the effect of a true semi-infinite solid is taken into account by a nonlocal potential via the embedding method, while the realistic Al(100) surface is modeled by a slab of five metal layers. In this latter case a dilute enough coverage of Fe is considered for comparison with the results of the isolated adatom on jellium. The full potential linearized augmented plane-wave method within an ab initio density-functional theory framework is used to describe the atoms in both approaches. Our calculations show that the electronic properties such as charge densities, densities of states, and the adatom magnetic moments of both models are in very good agreement. These results, corroborated by further calculations for a Co adatom, suggest that a relationship between the adatom magnetic moment and the local unperturbed charge density of the substrate exists, at least for simple metals. So a surface effective-medium approach for the adatom magnetic moments is proposed. The validity of such a method for 3d adatoms on noble metals is shown by comparison of surface jellium calculations with existing ones.
Physical Review B, 1996
An embedding method is proposed, based upon Green-function matching, for calculating the electron... more An embedding method is proposed, based upon Green-function matching, for calculating the electronic properties of an isolated adsorbate. The self-consistent single-particle Schrödinger equation is solved in a localized region containing the adsorbate and that part of the substrate mainly perturbed by it. The extended substrate is taken into account exactly by an effective embedding potential. The advantages of the method
Physical Review B, 2002
The induced surface resistivity rhos of 3d adatoms is calculated on a semi-infinite Al-like jelli... more The induced surface resistivity rhos of 3d adatoms is calculated on a semi-infinite Al-like jellium within the density-functional theory in the local-spin-density approximation (LSDA). The unexpected nonmonotonic behavior of rhos, as function of the position of the atoms with respect to the surface, recently found for most of 3d adatoms in calculations without spin polarization in the local-density approximation (LDA), is confirmed. However, the intensity and the dependence on the atomic number of rhos is modified by the LSDA in a significant way. At the equilibrium adsorption site on clean Al, the largest resistivity is found for Fe, not for Cr, which is different from the LDA results. The relationship between the maxima of rhos, the magnetic moment and the density of states induced by the adatom on the surface is discussed.
Physical Review B, 2001
In this work we perform a full ab initio density-functional theory calculation, within the embedd... more In this work we perform a full ab initio density-functional theory calculation, within the embedding method, of the Auger spectra of atomic impurities both inside a metal bulk and just inside the solid surface and chemisorbed on it. We consider a Na atom on and in a jellium-Ag host. In particular, the Auger spectra of the electronic transitions KL1V and
Physical Review Letters, 2004
The line shape of the Auger decay of adatoms is studied by a joint theoretical and experimental e... more The line shape of the Auger decay of adatoms is studied by a joint theoretical and experimental effort, the former within a DFT framework, and the latter with synchrotron radiation measurements. We investigate the KL(2,3)V Auger deexcitation of Na on Al(111), a system with different adsorption geometries. In particular, we study the (sqrt[3]xsqrt[3])R30 degrees phase at 1/3 ML (monolayer) and the more complex (2 x 2) structure at 1/2 ML coverage. From the comparison between theory and experiment, we unambiguously determine features that allow for the determination of the adsorption environment from the adatom Auger spectrum.
Physical Review B, 2009
ABSTRACT The spin polarization of the emitted electrons from 3d impurities in simple metal hosts ... more ABSTRACT The spin polarization of the emitted electrons from 3d impurities in simple metal hosts in a core-valence-valence Auger process is analyzed in terms of a first-principles density-functional theory approach, by using the golden rule. The relationship between the spin-dependent local density of states, the magnetic moments of the 3d atoms and the energy-dependent and total spin polarization of the Auger electrons is discussed. It is shown how to estimate the magnetic moment of the impurities from a measure of the total spin polarization of the Auger electrons. This can be achieved considering (i) that the Auger signal is simply due to the impurities only, (ii) the very locality of the Auger phenomenon, and (iii) a simple and general relationship between the spin polarization and the magnetic moment of the impurity which we show to be independent of the metal host.
Physical Review B, 2008
We propose an ab initio method to evaluate the core-valence-valence (CVV) Auger spectrum of syste... more We propose an ab initio method to evaluate the core-valence-valence (CVV) Auger spectrum of systems with filled valence bands. The method is based on the Cini-Sawatzky theory, and aims at estimating the parameters by first-principles calculations in the framework of density-functional theory (DFT). Photoemission energies and the interaction energy for the two holes in the final state are evaluated by performing DFT simulations for the system with varied population of electronic levels. Transition matrix elements are taken from atomic results. The approach takes into account the non-sphericity of the density of states of the emitting atom, spin-orbit interaction in core and valence, and non quadratic terms in the total energy expansion with respect to fractional occupation numbers. It is tested on two benchmark systems, Zn and Cu metals, leading in both cases to L 23 M 45 M 45 Auger peaks within 2 eV from the experimental ones. Detailed analysis is presented on the relative weight of the various contributions considered in our method, providing the basis for future development. Especially problematic is the evaluation of the hole-hole interaction for systems with broad valence bands: our method underestimates its value in Cu, while we obtain excellent results for this quantity in Zn.
Physical Review B, 2010
We have investigated the formation of scanning tunneling microscopy (STM) atomically resolved ima... more We have investigated the formation of scanning tunneling microscopy (STM) atomically resolved images of the Fe(001)-p(1×1)O surface. The latter is characterized by a high in-plane symmetry for both oxygen and iron atoms, thus representing a very appealing template for understanding how to distinguish between oxygen and metal atoms in STM images of an oxidized metal surface. We report on the
Physical Review B, 2010
We have investigated the formation of scanning tunneling microscopy (STM) atomically resolved ima... more We have investigated the formation of scanning tunneling microscopy (STM) atomically resolved images of the Fe(001)-p(1×1)O surface. The latter is characterized by a high in-plane symmetry for both oxygen and iron atoms, thus representing a very appealing template for understanding how to distinguish between oxygen and metal atoms in STM images of an oxidized metal surface. We report on the
Physical Review B, 2002
ABSTRACT By using a jellium model surface and a realistic one, the magnetic properties of a singl... more ABSTRACT By using a jellium model surface and a realistic one, the magnetic properties of a single Fe adatom on Al are studied. For the jellium surface the effect of a true semi-infinite solid is taken into account by a nonlocal potential via the embedding method, while the realistic Al(100) surface is modeled by a slab of five metal layers. In this latter case a dilute enough coverage of Fe is considered for comparison with the results of the isolated adatom on jellium. The full potential linearized augmented plane-wave method within an ab initio density-functional theory framework is used to describe the atoms in both approaches. Our calculations show that the electronic properties such as charge densities, densities of states, and the adatom magnetic moments of both models are in very good agreement. These results, corroborated by further calculations for a Co adatom, suggest that a relationship between the adatom magnetic moment and the local unperturbed charge density of the substrate exists, at least for simple metals. So a surface effective-medium approach for the adatom magnetic moments is proposed. The validity of such a method for 3d adatoms on noble metals is shown by comparison of surface jellium calculations with existing ones.
Physical Review B, 1996
An embedding method is proposed, based upon Green-function matching, for calculating the electron... more An embedding method is proposed, based upon Green-function matching, for calculating the electronic properties of an isolated adsorbate. The self-consistent single-particle Schrödinger equation is solved in a localized region containing the adsorbate and that part of the substrate mainly perturbed by it. The extended substrate is taken into account exactly by an effective embedding potential. The advantages of the method
Physical Review B, 2002
The induced surface resistivity rhos of 3d adatoms is calculated on a semi-infinite Al-like jelli... more The induced surface resistivity rhos of 3d adatoms is calculated on a semi-infinite Al-like jellium within the density-functional theory in the local-spin-density approximation (LSDA). The unexpected nonmonotonic behavior of rhos, as function of the position of the atoms with respect to the surface, recently found for most of 3d adatoms in calculations without spin polarization in the local-density approximation (LDA), is confirmed. However, the intensity and the dependence on the atomic number of rhos is modified by the LSDA in a significant way. At the equilibrium adsorption site on clean Al, the largest resistivity is found for Fe, not for Cr, which is different from the LDA results. The relationship between the maxima of rhos, the magnetic moment and the density of states induced by the adatom on the surface is discussed.
Physical Review B, 2001
In this work we perform a full ab initio density-functional theory calculation, within the embedd... more In this work we perform a full ab initio density-functional theory calculation, within the embedding method, of the Auger spectra of atomic impurities both inside a metal bulk and just inside the solid surface and chemisorbed on it. We consider a Na atom on and in a jellium-Ag host. In particular, the Auger spectra of the electronic transitions KL1V and
Physical Review Letters, 2004
The line shape of the Auger decay of adatoms is studied by a joint theoretical and experimental e... more The line shape of the Auger decay of adatoms is studied by a joint theoretical and experimental effort, the former within a DFT framework, and the latter with synchrotron radiation measurements. We investigate the KL(2,3)V Auger deexcitation of Na on Al(111), a system with different adsorption geometries. In particular, we study the (sqrt[3]xsqrt[3])R30 degrees phase at 1/3 ML (monolayer) and the more complex (2 x 2) structure at 1/2 ML coverage. From the comparison between theory and experiment, we unambiguously determine features that allow for the determination of the adsorption environment from the adatom Auger spectrum.
Physical Review B, 2009
ABSTRACT The spin polarization of the emitted electrons from 3d impurities in simple metal hosts ... more ABSTRACT The spin polarization of the emitted electrons from 3d impurities in simple metal hosts in a core-valence-valence Auger process is analyzed in terms of a first-principles density-functional theory approach, by using the golden rule. The relationship between the spin-dependent local density of states, the magnetic moments of the 3d atoms and the energy-dependent and total spin polarization of the Auger electrons is discussed. It is shown how to estimate the magnetic moment of the impurities from a measure of the total spin polarization of the Auger electrons. This can be achieved considering (i) that the Auger signal is simply due to the impurities only, (ii) the very locality of the Auger phenomenon, and (iii) a simple and general relationship between the spin polarization and the magnetic moment of the impurity which we show to be independent of the metal host.
Physical Review B, 2008
We propose an ab initio method to evaluate the core-valence-valence (CVV) Auger spectrum of syste... more We propose an ab initio method to evaluate the core-valence-valence (CVV) Auger spectrum of systems with filled valence bands. The method is based on the Cini-Sawatzky theory, and aims at estimating the parameters by first-principles calculations in the framework of density-functional theory (DFT). Photoemission energies and the interaction energy for the two holes in the final state are evaluated by performing DFT simulations for the system with varied population of electronic levels. Transition matrix elements are taken from atomic results. The approach takes into account the non-sphericity of the density of states of the emitting atom, spin-orbit interaction in core and valence, and non quadratic terms in the total energy expansion with respect to fractional occupation numbers. It is tested on two benchmark systems, Zn and Cu metals, leading in both cases to L 23 M 45 M 45 Auger peaks within 2 eV from the experimental ones. Detailed analysis is presented on the relative weight of the various contributions considered in our method, providing the basis for future development. Especially problematic is the evaluation of the hole-hole interaction for systems with broad valence bands: our method underestimates its value in Cu, while we obtain excellent results for this quantity in Zn.
Physical Review B, 2010
We have investigated the formation of scanning tunneling microscopy (STM) atomically resolved ima... more We have investigated the formation of scanning tunneling microscopy (STM) atomically resolved images of the Fe(001)-p(1×1)O surface. The latter is characterized by a high in-plane symmetry for both oxygen and iron atoms, thus representing a very appealing template for understanding how to distinguish between oxygen and metal atoms in STM images of an oxidized metal surface. We report on the
Physical Review B, 2010
We have investigated the formation of scanning tunneling microscopy (STM) atomically resolved ima... more We have investigated the formation of scanning tunneling microscopy (STM) atomically resolved images of the Fe(001)-p(1×1)O surface. The latter is characterized by a high in-plane symmetry for both oxygen and iron atoms, thus representing a very appealing template for understanding how to distinguish between oxygen and metal atoms in STM images of an oxidized metal surface. We report on the