The physical and chemical properties of cluster systems at the subnano and nanoscale are often found to differ from those of the bulk and display a unique dependence on size, geometry, and composition. Indeed, most interesting are systems which have properties that vary discontinuously with the number of atoms and composition, rather than scale linearly with size. This realm of cluster science where “one atom makes a difference” is undergoing an explosive growth in activity, and as a result of extensive collaborative activities through theory at VCU and experiment at PSU, our groups are recognized as pioneers in this area in which we have been active for many years. Herein we provide an overview of the field with primary focus on our joint undertakings which have spawned the superatom concept, giving rise to a 3-D periodic table of cluster elements and the prospect of using these as building blocks of new nanoscale materials with tailored properties.

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Articles you may be interested inA threshold-based approach to calorimetry in helium droplets: Measurement of binding energies of water clusters Rev. Sci. Instrum. 83, 073109 (2012); 10.1063/1.4738664 Effects of binding energy on exchange contributions to the stopping of electrons AIP Conf. Accurate structures and binding energies for small water clusters: The water trimer J. Chem. Phys. 110, 9435 (1999); 10.1063/1.478908Structures, binding energies, and spectra of isoenergetic water hexamer clusters: Extensive ab initio studiesThe binding energies of water cluster cations are obtained by measuring decay fractions of metastable dissociation and employing Klots' model of evaporative dissociation. Their variation with degree of solvation shows the commonly observed decrease, followed by a slow rise in magnitude, which typifies the trend found for solvated cations. There is no observed abrupt change in the vicinity of the well-known magic number (H 2 0hl' H+ corresponding to (H 2 0)20' H30+. Other data are used to deduce free energies for water clusters up to size n=28, allowing a determination of entropy changes with size. All of the thermochemical data, including prior literature values, are assessed in terms of calculations made using the liquid drop model and standard statistical mechanical equations. It is concluded that entropic rather than energetic effects give rise to the referred to magic number.

Erratum: "Ligand and metal binding energies in platinum carbonyl cluster anions: Collision-induced dissociation of Pt m − and Pt m (CO) n " [J. Gas-phase thermochemical stabilities of cluster ions [( N 2 ) m ( Ar ) n ] + with (m+n)=1-5 Unimolecular dissociation of trivalent metal cluster ions: The size evolution of metallic bonding Ligand and metal binding energies in platinum carbonyl cluster anions: Collision-induced dissociation of Pt m − and Pt m ( CO ) n −The formation and structure of gas-phase vanadium oxide cluster anions are examined using a guided ion beam mass spectrometer coupled with a laser vaporization source. The dominant peaks in the anion total mass distribution correspond to clusters having stoichiometries of the formϪ , and V 7 O 16-18Ϫ indicate that VO 2 , VO 3 , and V 2 O 5 units are the main building blocks of these clusters. There are many similarities between the anion mass distribution and that of the cation distribution studied previously. The principal difference is a shift to higher oxygen content by one additional oxygen atom for the stoichiometric anions (V x O y Ϫ ) as compared to the cations with the same number of vanadium atoms, which is attributed to the extra pair of electrons of the anionic species. The oxygen-rich clusters, V x O y ͑O 2 ͒ Ϫ , are shown to more tightly adsorb molecular oxygen than those of the corresponding cationic clusters. In addition, the bond dissociation thresholds for the vanadium oxide clusters ⌬E(V ϩ -O)ϭ6.09 Ϯ0.28 eV, ⌬E(OV ϩ -O)ϭ3.51Ϯ0.36 eV, and ⌬E(O 2 V Ϫ -O)ϭ5.43Ϯ0.31 eV are determined from the energy-dependent collision-induced dissociation cross sections with Xe as the collision partner. To the best of our knowledge, this is the first bond dissociation energy reported for the breaking of the V-O bond of a vanadium oxide anion.

Findings of magic peaks corresponding to M(8)C(12)(+) (M = V, Zr, and Hf) formed from reactions of the respective metals with various small hydrocarbons, in conjunction with recent findings for the titanium system, establish metallo-carbohedrenes as a stable general class of molecular cluster ions. A dodecahedral structure of T(h) point symmetry accounts for the stability of these ionic clusters.