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The electronic structure of isolated bis(phthalocyaninato) terbium(III) molecules, a novel single-molecular-magnet (SMM), supported on the Cu(111) surface has been characterized by density functional theory and scanning tunneling spectroscopy. These studies reveal that the interaction with the metal surface preserves both the molecular structure and the large spin magnetic moment of the metal center. The 4f electron states are not perturbed by the adsorption while a strong molecular/metal interaction can induce the suppression of the minor spin contribution delocalized over the molecular ligands. The calculations show that the inherent spin magnetic moment of the molecule is only weakly affected by the interaction with the surface and suggest that the SMM character might be preserved.The miniaturization of information storage devices drives the search for new nanoscale magnetic materials. Single molecular magnets (SMMs) formed by metal-organic complexes are very promising candidates as their large spin ground-state and large magnetic anisotropy are characteristics of each isolated molecule.1 Moreover, these systems provide a natural playground to explore magnetism at the nanoscale. Their future technological applications, such as quantum computing and high-density magnetic storage devices, are presently hampered by the difficulty of adsorbing SMMs onto surfaces and, quite importantly, by the lack of understanding on whether their magnetic properties are modified upon adsorption. In particular, the nonapplicability of conventional techniques, which allow an in-vacuum deposition, has so far hindered the systematic study of individual molecular magnets on surfaces. Solution-based deposition techniques including drop casting, 2,3 Langmuir-Blodgett, 4 microcontact printing, 5 covalent Au-S attaching, 6 and surface functionalization 7 have been successfully used to transfer molecules to surfaces but the magnetic properties of the adsorbed molecules have so far not been demonstrated. 3 This has tentatively been assigned to an induced local disorder caused by the used deposition techniques or by the coupling to the surface. 8 In this letter, we describe the structural, magnetic and electronic properties of a surface-supported SMM by combining scanning tunneling microscopy (STM) and spectroscopy (STS) with numerical simulations based on density functional theory (DFT). Topographic images and conductance maps of isolated SMM (namely bis(phthalocyaninato) terbium(III)) achieved at several energies confirm that the molecular structure is unchanged by the interaction with the surface. The Tb-4f electron states, which are responsible for the large magnetic moment of the molecular magnet, are little affected by molecular adsorption on the metal surface. Thus, it can be expected that the SMM character of the surface supported bis(phthalocyaninato) terbium(III) (abbreviated by TbPc2) molecules is preserved.TbPc2 molecules represent the first example of mononuclear metal complexes behaving as SMMs (i.e., showing large mag...

We investigate electronic and optical properties of the topological Weyl semimetals TaAs, TaP, NbAs and NbP crystallizing in bct geometry by means of the ab initio density functional theory with spin-orbit interaction within the independent-particle approximation. The small energetical overlap of Ta5d or Nb4d derived conduction and valence bands leads to electron and/or hole pockets near the Fermi energy at the 24 Weyl nodes. The nodes give rise to two-(three-)dimensional Dirac cones for the W1 (W2) Weyl type. The band dispersion and occupation near the Weyl nodes determine the infrared optical properties. They are dominated by interband transitions, which lead to a deviation from the expected constant values of the imaginary part of the dielectric function. The resulting polarization anisotropy is also visible in the real part of the optical conductivity, whose lineshape deviates from the expected linearity. The details of the Weyl nodes are discussed in relation to recent ARPES results for TaAs and NbP, and compared with measured optical spectra for TaAs. The spectral features of the anisotropic and tilted Weyl fermions are restricted to low excitation energies above absorption onsets due to the band occupation.

We study the electronic properties of two-dimensional (2D) group-III nitrides BN, AlN, GaN, InN, and TlN by first-principles approaches. With increasing group-III atomic number, a decrease of the electronic gap from 6.7 eV to 0 eV takes place. 2D GaN and 2D InN in honeycomb geometry present a direct gap at Γ, while the honeycomb structures of BN and AlN tend to be indirect semiconductors with the valence band maximum at K. Alloying of the nitrides allows tuning the gap with cation composition. Interestingly, Inx Ga1-xN and Inx Tl1-xN alloys enable, with varying x, to construct type I or type II heterostructures. We demonstrate that it is possible to tailor the electronic and optical response from UV to IR. We suggest that 2D InGaN and InTlN heterostructures may efficiently harvest light and serve as building blocks for a future generation of III-V solar cells. Finally, 2D InTlN with a low In content is eligible as the emitter and detector for THz applications

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The yellowing of paper on aging causes major aesthetic damages of cultural heritage. It is due to cellulose oxidation, a complex process with many possible products still to be clarified. By comparing ultraviolet-visible reflectance spectra of ancient and artificially aged modern papers with ab initio time-dependent density functional theory calculations, we identify and estimate the abundance of oxidized functional groups acting as chromophores and responsible of paper yellowing. This knowledge can be used to set up strategies and selective chemical treatments preventing paper yellowing.

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Both ozone (O3) and drought can limit carbon fixation by forest trees. To cope with drought stress, plants have isohydric or anisohydric water use strategies. Ozone enters plant tissues through stomata. Therefore, stomatal closure can be interpreted as avoidance to O3 stress. Here, we applied an optimization model of stomata involving water, CO2, and O3 flux to test whether isohydric and anisohydric strategies may affect avoidance of O3 stress by stomatal closure in four Mediterranean tree species during drought. The data suggest that stomatal closure represents a response to avoid damage to the photosynthetic mechanisms under elevated O3 depending on plant water use strategy. Under high‐O3 and well‐watered conditions, isohydric species limited O3 fluxes by stomatal closure, whereas anisohydric species activated a tolerance response and did not actively close stomata. Under both O3 and drought stress, however, anisohydric species enhanced the capacity of avoidance by closing stomata to cope with the severe oxidative stress. In the late growing season, regardless of the water use strategy, the efficiency of O3 stress avoidance decreased with leaf ageing. As a result, carbon assimilation rate was decreased by O3 while stomata did not close enough to limit transpirational water losses.