Anomalously large $g$-factor of single atoms adsorbed on a metal substrate
Jens WiebeAlexander A. KhajetooriansBruno ChilianR. WiesendangerSamir LounisA. T. CostaDouglas Mills
4
Citation
0
Reference
20
Related Paper
Citation Trend
Keywords:
Factor (programming language)
Cite
Chemisorption
Cite
Citations (21)
Evaporation of Cs atoms onto dehydrated polycrystalline MgO leads to the formation of surface color centers in correspondence of surface point defects. EPR spectroscopy has revealed that the adsorbed Cs atoms are partially ionized, and a fraction of the electron spin density is delocalized onto a surface oxygen vacancy or trap. The observed defect can thus be written as Csδ+(trap) δ- . These results give evidence of the preferential interaction of the metal atoms with specific surface defect sites in the early stages of the metal−support interaction. The reaction of these centers with molecular oxygen leads to bleaching of the surface with formation of the O2- superoxide radical anion. A fraction of the adsorbed superoxide ions are adsorbed on "regular" Mg2+ sites while the remaining ones are adsorbed on top of Cs+ ions.
Cite
Citations (12)
Journal of the Chemical Society Faraday Transactions 1 Physical Chemistry in Condensed Phases (1975)
The surface potential of adsorbed hydrogen on evaporated platinum films has been measured as a function of temperature and amount adsorbed. For films prepared by condensation at 78 K, three different adsorbed species are identified, an electronegative and an electropositive adatom and, at higher pressures, an electropositive molecular species. The electronegative form has a higher sticking probability, the largest10 heat of chemisorption (71 kJ mol–1) and is confined to high-index planes; the electropositive adatoms have a lower heat of 36 kJ mol–1 and the molecular species one of 5 kJ mol–1. The dipole moments are in the ratio: –1.0 : + 1.3 : + 0.57. Previous, apparently conflicting, results of other workers who have identified only two adspecies can now be reconciled. On films formed by condensation at 273 K, the adsorption of the electronegative species is much less owing to the decreasing extent of high-index planes.
Chemisorption
Hydrogen molecule
Cite
Citations (27)
First-principles calculations within the density functional theory (DFT) have been addressed to study the energetic stability, and electronic properties of alkali and alkali-earth atoms adsorbed on a silicon carbide (SiC) single layer. We observe that all atoms are most stable (higher binding energy) on the top of a Si atom, which moves out of the plane (in the opposite direction to the adsorbed atom). Alkali atoms adsorbed give raise to two spin unpaired electronic levels inside the band gap leading the SiC single layer to exhibit n-type semiconductor properties. For alkaline atoms adsorbed there is a deep occupied spin paired electronic level inside the band gap. These finding suggest that the adsorption of alkaline and alkali-earth atoms on SiC layer is a powerful feature to functionalize two dimensional SiC structures, which can be used to produce new electronic, magnetic and optical devices as well for hydrogen and oxygen evolution reaction (HER and OER, respectively). Furthermore, we observe that the adsorption of H2 is ruled by dispersive forces (van der Waals interactions) while the O2 molecule is strongly adsorbed on the functionalized system.
Alkaline earth metal
Cite
Citations (23)
Chemisorption
Cite
Citations (36)
On the basis of first-principles total-energy calculations, the magnetic property of O-terminated ZnO(0001) surfaces adsorbed with different molecules (NH3, H2S, and H2O) is studied. NH3 is adsorbed above Zn sites. A magnetic moment distribution occurs because of the formation of N 2p holes with minority spin states in NH3, which results from a charge transfer from NH3 to the ZnO(0001) surface. Furthermore, the ZnO(0001) surface adsorbed with NH3 prefers ferromagnetism. On the other hand, due to the decomposition of H2S on the ZnO(0001) surface, magnetic moments appear that mainly exist on the S atom and its neighboring atoms, whereas there are no magnetic moments in ZnO(0001) adsorbed with H2O. The interaction between molecules and the ZnO surface results in the unsaturated outer shells of the N atom in NH3 and the S atom in H2S, and as a result, magnetism of the molecule-adsorbed ZnO(0001) surface comes into being. Results indicate that the electronegativity of the atoms in the molecules and at the surface may be an important factor for the origin of magnetic moments and may provide a general explanation for the occurrence of ferromagnetic properties in molecule-enwrapped oxide nanoparticles.
Magnetism
Electronegativity
Cite
Citations (36)
Cite
Citations (7)
Density functional theory has been performed to investigate the chemisorption and diffusion of H atoms on the surface of single-walled carbon nanotubes (SWNTs). The results show that the binding energy of a single hydrogen atom on the SWNTs surface decreases as the diameter of the tube increases and is not affected by the chirality of the tube much. Two hydrogen atoms favor binding at adjacent and opposite positions rather than at alternate carbon site. As for the diffusion of H atoms on the tube, it is found that an isolated H atom can diffuse rather than desorb on the small SWNT upon heating. As the tube diameter increases, the diffusion barrier for H atom on the surface decreases. Further study shows that when the H atom diffuses around another H atom, the diffusion barriers vary with the relative sites of the two H atoms.
Chemisorption
Hydrogen atom
Carbon fibers
Surface diffusion
Carbon atom
Cite
Citations (4)
Nanoclusters
Cite
Citations (7)
Porous graphene (PG), a kind of graphene-related material with nanopores in the graphene plane, exhibits novel properties different from those of pristine graphene, leading to its potential applications in many fields. Owing to periodic nanopores existing naturally in the two-dimensional layer, PG can be used as an ideal candidate for hydrogen storage material. High hydrogen storage capacity of Li-decorated PG has been investigated theoretically, but the effect of temperature on the stability of the H<sub>2</sub> adsorbed on Li-PG has been not discussed yet. In this paper, by using the first-principles method, the hydrogen storage capacity on alkaline metal atoms (Li, Na, K) decorated porous graphene is investigated in depth with generalized gradient approximation, and the effect of the temperature on the stability of the hydrogen adsorption system is elucidated by the <i>ab initio</i> molecular-dynamics simulation. The results show that the most favorable adsorption sites of Li, Na and K are the hollow center sites of the C hexagon, and four alkaline metal atoms can be adsorbed stably on both sides of PG unit cell without clustering. Alkaline metal adatoms adsorbed on PG become positively charged by transferring charge to PG and adsorbed H<sub>2</sub> molecules, and three H<sub>2</sub> molecules can be adsorbed around each alkaline metal atom. By analyzing the Mulliken atomic populations, charge density differences and density of states of H<sub>2</sub> adsorbed on Li-PG system, we find that the H<sub>2</sub> molecules are adsorbed on alkaline metal atoms decorated graphene complex by attractive interaction between positively charged alkaline metal adatoms and negatively charged H and weak van der Waals interaction. Twelve H<sub>2</sub> molecules are adsorbed on both sides of PG decorated with alkaline metal atoms. The average adsorption energy of H<sub>2</sub> adsorbed on Li-PG, Na-PG and K-PG are –0.246, –0.129 and –0.056 eV/H<sub>2</sub>, respectively. It is obvious that the hydrogen adsorption capacity of Li-PG system is strongest, and the hydrogen adsorption capacity of K-PG is weakest, thus K-PG structure is not suitable for hydrogen storage. Furthermore, by the <i>ab initio</i> molecular-dynamic simulation, in which the NVT ensemble is selected but the external pressure is not adopted, the effect of temperature on the stability of H<sub>2</sub> molecules adsorbed on Li-PG system is elucidated. The result shows that the configuration of Li-PG is very stable, H<sub>2</sub> molecules are stably adsorbed around the Li atoms at low temperature, and some H<sub>2</sub> molecules start to be desorbed from the Li atoms with the increase of temperature. At 200 K, H<sub>2</sub> molecules begin to move away from Li atoms, and two H<sub>2</sub> molecules escape from the binding of the Li atoms at 250 K. At 300 K, nine H<sub>2</sub> molecules can be stably absorbed on both sides of Li-PG, and the gravimetric hydrogen storage capacity can reach up to 9.25 wt.%, which is much higher than the the US Department of Energy target value of 5.5 wt.% for the year 2017. With the increase of temperature, more adsorbed H<sub>2</sub> molecules are desorbed, seven H<sub>2</sub> molecules can be desorbed at 400 K, and all H<sub>2</sub> molecules are completely desorbed in a temperature range of 600–700 K.
Cite
Citations (8)