The Electronic and Magnetic Properties of a Few Transition-Metal Clusters

Structural determination of neutral Co n clusters (n = 4-10,13) through IR-UV two-color vibrational spectroscopy and DFT calculations

We recorded IR spectra for neutral cobalt clusters via two-color IR-UV ionization, using the Free Electron Laser for intracavity experiments (FELICE). Well-resolved IR spectra are presented for [Formula: see text] (n  =  4-10, 13) and analyzed with the help of Density Functional Theory calculations using two different correlation exchange functionals: the revisited Tao-Perdew-Staroverov-Scuseria (revTPSS) and the frequently used Perdew-Burke-Ernzerhof (PBE) approaches. Although we have not performed an extensive structure search, we tentatively assign the spectra for all cluster sizes except for n  =  7, and n  =  10. We find that neither of the two functionals chosen clearly outperforms the other in predicting IR spectra, and that relatively low scaling factors of 0.82 (PBE) and 0.8 (revTPSS) are required. In contrast to the magnetic moments, the calculated electric dipole moments fluctuate strongly as a function of cluster size and could therefore be used as an indirect probe to the cluster structure.

Multiferroic rhodium clusters

Simultaneous magnetic and electric deflection measurements of rhodium clusters (Rh(N), 6 ≤ N ≤ 40) reveal ferromagnetism and ferroelectricity at low temperatures, while neither property exists in the bulk metal. Temperature-independent magnetic moments (up to 1 μ(B) per atom) are observed, and superparamagnetic blocking temperatures up to 20 K. Ferroelectric dipole moments on the order of 1D with transition temperatures up to 30 K are observed. Ferromagnetism and ferroelectricity coexist in rhodium clusters in the measured size range, with size-dependent variations in the transition temperatures that tend to be anticorrelated in the range n = 6-25. Both effects diminish with size and essentially vanish at N = 40. The ferroelectric properties suggest a Jahn-Teller ground state. These experiments represent the first example of multiferroic behavior in pure metal clusters.

OXYGEN PARTIAL PRESSURE AND SUBSTRATE BIAS VOLTAGE INFLUENCED STRUCTURAL, ELECTRICAL AND OPTICAL PROPERTIES OF RF MAGNETRON SPUTTERED Ag2Cu2O3 FILMS

Ag2Cu2O3 films were deposited on glass substrates held at 303 K by RF magnetron sputtering of Ag70 Cu30 target at different oxygen partial pressures and substrate bias voltages. Single phase Ag2Cu2O3 films were formed at an oxygen partial pressure of 2 × 10-2 Pa . The films deposited at oxygen partial pressure 2 × 10-2 Pa and substrate bias voltage of -60 V were nanocrystalline with crystallite size of 20 nm, low electrical resistivity of 3.9 Ωcm and optical band gap of 2.02 eV.

Density functional study of structural, electronic, and optical properties of small bimetallic ruthenium-copper clusters

The structural, electronic, bonding, magnetic, and optical properties of bimetallic [Cu(n)Ru(m)](+/0/-) (n + m ≤ 3; n, m = 0-3) clusters were computed in the framework of the density functional theory (DFT) and time-dependent DFT (TD-DFT) using the full-range PBE0 nonlocal hybrid GGA functional combined with the Def2-QZVPP basis sets. Several low-lying states have been investigated and the stability of the ground state spinomers was estimated with respect to all possible fragmentation schemes. Molecular orbital and population analysis schemes along with computed electronic parameters illustrated the details of the bonding mechanisms in the [Cu(n Ru(m)](+/0/-) clusters. The TD-DFT computed UV-visible absorption spectra of the bimetallic clusters have been fully analyzed and assignments of all principal electronic transitions were made and interpreted in terms of contribution from specific molecular orbital excitations.