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Oxidation Effects of the Small Chromium and Manganese Cluster Ions K. Tono, 1,2 A. Terasaki, 2 T. Ohta, 1 and T. Kondow 2 1 Department of Chemistry, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan 2 Cluster Research Laboratory, Toyota Technological Institute in East Tokyo Laboratory, Genesis Research Institute, Inc., 717-86 Futamata, Ichikawa, Chiba 272-0001, Japan Properties of transition-metal clusters are affected by reaction with foreign elements such as nitrogen and oxygen. For example, it has been predicted that the magnetic property of a chromium dimer is drastically changed by either nitridation or oxidation [1,2]. Motivated by these theoretical studies, we investigated the electronic structures of the chromium- and manganese-oxide cluster anions through measurements of photoelectron spectra and analyses with the aid of the density functional theory (DFT). It was found that the spin magnetic moment of Cr2O – is as large as 9 µB, while that of Cr2 – is 1 µB. This result shows that the spin coupling between the chromium sites becomes ferromagnetic upon oxidation of Cr2 – whose chromium sites are coupled antiferromagnetically [3,4]. The mechanism of the ferromagnetic spin coupling is explained on the basis of the geometric and electronic structures obtained by the DFT calculations. The oxygen atom at the bridge site weakens the strong bond between the chromium atoms, which is responsible for the antiferromagnetic coupling in Cr2 – . In addition, significant hybridization between chromium 3d and oxygen 2p orbitals allows electrons in the same spin state to be transferred from the two chromium atoms to the oxygen atom. Consequently the local spins on the chromium sites are bound to form a ferromagnetic coupling in a similar scheme of the superexchange interaction encountered in solids. An oxidation effect of a similar kind was found for Mn2O – , in which a ferromagnetic coupling between the local spins (about 5.5 µB) at the manganese sites stabilizes its electronic structure [5,6]. Manganese clusters differ distinctly from chromium clusters; the manganese atoms are very weakly bound because of the closed shell of 4s electrons. This is also true to singly charged manganese cluster cations, MnN + (N=3–7), where the binding energy is found to be less than 1 eV/atom as reported in Ref. [7] and as shown further by the present measurements. The structural specificity results from a weak van-der-Waals like interaction between the constituent atoms, and is likely to change greatly if one introduces an oxygen atom into MnN + , because the oxygen could glue manganese atoms in its vicinity. Actually we elucidated how the introduced oxygen changes the geometrical and electronic structures of MnN + in photodissociation experiments of MnNO + (N=3–5). In practice, the mass spectra of photodissociation products from MnNO + were measured as a function of the photon energy of an excitation laser. The results show that the oxygen atom and two manganese atoms form a Mn2O + core ion and the other manganese atoms are weakly bound to the core ion. Analyses of the photodissociation action spectra of MnNO + are now in progress in order to obtain detailed information on the electronic and geometric structures. References [1] S. E. Weber, B. V. Reddy, B. K. Rao, and P. Jena, Chem. Phys. Lett. 295, 175 (1998). [2] B. V. Reddy and S. N. Khanna, Phys. Rev. Lett. 83, 3170 (1999). [3] K. Tono, A. Terasaki, T. Ohta, and T. Kondow, Phys. Rev. Lett. 90, 133402 (2003). [4] K. Tono, A. Terasaki, T. Ohta, and T. Kondow, J. Chem. Phys. 119, 11221 (2003). [5] K. Tono, A. Terasaki, T. Ohta, and T. Kondow, Chem. Phys. Lett. 388, 374 (2004). [6] S. N. Khanna, P. Jena, W.-J. Zheng, J. M. Nilles, and K. H. Bowen, Phys. Rev. B 69, 144418 (2004). [7] A. Terasaki, S. Minemoto, and T. Kondow, J. Chem. Phys. 117, 7520 (2002). 21
22 Electronic structure and spin polarization of dilute magnetic semiconducting nanocrystals: a first principles approach Xiangyang Huang 1 , Adi Makmal 2 , James R. Chelikowsky 1 , and Leeor Kronik 2 1 Department of Chemical Engineering and Materials Science and the Institute for the Advanced Theory of Information Materials, University of Minnesota, Minneapolis 55455, USA 2 Department of Materials and Interfaces, Weizmann Institute of Science, Rehovoth 76100, Israel. Bulk dilute magnetic semiconductors have attracted considerable attention in recent years because they exhibit semiconducting and magnetic properties at the same time, potentially enabling novel electronic devices that manipulate the electron spin in addition to its charge, commonly known as “spintronic” devices. 1 Novel spintronic effects are expected at nanocrystalline dilute magnetic semiconductors because the carrier confinement greatly enhances spin-spin interactions. Here, we present what we believe to be the first ab initio study of the electronic structure of Mncontaining Ge, GaAs, and ZnSe nanocrystals, using a real-space pseudopotential-density functional theory approach. We find that in all cases significant spin-polarization is formed and that the magnetic moment distribution around the Mn atom displays clear chemical trends, becoming more localized with increasing bond ionicity, as shown in Fig. 1. A detailed analysis of the electronic structure reveals different patterns of level filling and ferromagnetic or antiferromagnetic couplings. Importantly, the electronic structure exhibits considerable quantum size effects. The electronic and magnetic properties of the dilute magnetic nanocrystals are compared and contrasted with the properties of the corresponding bulk systems. Potential device implications are discussed. References Figure 1. Distribution of the net magnetic moment for (from left to right) passivated MnGe81,MnGa40As41, and MnZn40Se41 nanocrystals. [1] S. A. Wolf, D. D. Awschalom, R. A. Buhrman, J. M. Daughton, S. von Molnar, M. L. Roukes A. Y. Chtchelkanova, and D. M. Treger, Science 294, 1488 (2001).
Page 1 and 2: Symposium on Size Selected Clusters
Page 4: Table of Contents FULL LENGTH TALKS
Page 8 and 9: Metallic clusters and oxygen Cather
Page 10 and 11: Infrared Spectroscopy of Metal Ion
Page 12 and 13: Model Gold Catalysts by Size-Select
Page 14 and 15: Ultra-stable Hetero-nuclear Microcl
Page 16 and 17: Tailoring functionality of clusters
Page 18 and 19: The hydrogen transfer reaction: fro
Page 20 and 21: Atomic and Molecular Architecture a
Page 22 and 23: Magnetic Properties of Deposited Tr
Page 24 and 25: Cluster ferroelectricity Walt de He
Page 28 and 29: Electronic structure and bonding in
Page 30 and 31: Catalytic CO oxidation on ionic pla
Page 32 and 33: Melting, Pre-melting, and Glass Tra
Page 34 and 35: Vibrational Spectroscopy of Large S
Page 36 and 37: Novel Properties of Soft-Nano-Molec
Page 38: Posters 33
Page 42 and 43: Structure and Bonding in Carbon Clu
Page 44 and 45: Photoelectron Spectroscopy of Fulle
Page 46 and 47: Nucleation of single-walled carbon
Page 48: Chemistry 43
Page 51 and 52: 46 B - 8 Triplatinum carbonyl compl
Page 53 and 54: B - 10 48 Structural and Electronic
Page 55 and 56: B - 12 50 Size Dependent Carbon Mon
Page 57 and 58: B - 14 52 Binding energies of CO an
Page 59 and 60: B - 16 54 Reactivity of Size-Select
Page 61 and 62: B - 18 56 Oxygen adsorption at anio
Page 63 and 64: B - 20 Gold Clusters, CO-Chemisorbe
Page 65 and 66: B - 22 60 Probing the Electronic St
Page 67 and 68: B - 24 62 Joint theoretical and exp
Page 70 and 71: Photoionization Dynamics of Pure He
Page 72 and 73: Fast Electronic Relaxation in Metal
Page 74 and 75: Femtosecond photoelectron spectrosc
Page 76 and 77:
Signatures of the Giant Dipole Reso
Page 78 and 79:
Embedding of Na clusters in raregas
Page 80 and 81:
Theoretical studies of ultrafast pr
Page 82:
Magnetism 77
Page 85 and 86:
B - 38 80 Mn clusters: a nanoscale
Page 88 and 89:
Materials 83
Page 90 and 91:
Intensity 10000 8000 6000 4000 2000
Page 92 and 93:
Passivation, charging and optical p
Page 94:
WS and MoS: Magic Clusters and Nano
Page 98 and 99:
PEACE - a new photoelectron action
Page 100 and 101:
B - 47 Computational Electron Spect
Page 102 and 103:
Photoionisation using Kohn-Sham wav
Page 104:
Structural characterization of larg
Page 107 and 108:
A - 0 102
Page 109 and 110:
A - 2 104 Gold Clusters with Densit
Page 111 and 112:
A - 4 Structure Determination of Sm
Page 113 and 114:
A - 6 108 Mass Spectrometric Invest
Page 115 and 116:
A - 8 110 Probing the properties of
Page 117 and 118:
A - 10 112 Planar Boron Clusters an
Page 119 and 120:
A - 10 114
Page 121 and 122:
A - 12 116 Infrared Spectroscopy of
Page 123 and 124:
A - 14 118 Computational Study of (
Page 126 and 127:
Phase Transitions 121
Page 128 and 129:
Structural changes in small and med
Page 130 and 131:
Molecular Dynamics Simulations of t
Page 132 and 133:
Rare Gases 127
Page 134 and 135:
A - 20 Decay behaviour of dimer ion
Page 136 and 137:
High resolution electron ionization
Page 138:
Photodissociation of rare-gas trime
Page 141 and 142:
A - 24 136
Page 143 and 144:
A - 26 138 Sizedependence of Electr
Page 146 and 147:
Solvations 141
Page 148 and 149:
Ionization Potentials of Large Sodi
Page 150:
First principles studies on the rea
Page 153 and 154:
148
Page 155 and 156:
A - 32 150 Single Atom Dispersion o
Page 157 and 158:
A - 34 152 Supported Gold Clusters
Page 159 and 160:
A - 36 The Size-Evolution of the Op
Page 161 and 162:
A - 38 156 Transition From One- to
Page 163 and 164:
A - 40 158 Multiple Size-Selected C
Page 165 and 166:
A - 42 160 A comparative simulation
Page 167 and 168:
A - 44 DFT-Investigations of coales
Page 169 and 170:
A - 46 164 Mass-selected Nanocrysta
Page 172 and 173:
Author Index 167
Page 174 and 175:
Abbet, S...........................
Page 176 and 177:
Murakami, J........................
Page 178:
Time 8.30 a.m. 9.15 a.m. 10.00 a.m.
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Book of Abstracts Book of Abstracts - Universität Konstanz

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