Rutile TiO2 nanowhiskers have been synthesized by annealing a precursor powder in which NaCl and Ti(OH)4 particles were homogeneously mixed. The precursor powder was prepared by mixing three kinds of inverse microemulsions (μE) containing TiCl4 aqueous solution, ammonia, and NaCl aqueous solution, respectively, followed by washing with acetone. Annealing temperature and packing density of Ti(OH)4 in the precursor powder influenced the formation of rutile nanowhiskers. The optimum temperature was 750 °C. TiO2 nanowhiskers obtained by annealing a precursor powder in which the molar ratio of sodium to titanium was 400 at 750 °C for 2 h had diameters of 10–50 nm and lengths of several micrometers. They were straight rods with square cross sections, and the side surfaces were composed of four equivalent {110} planes.

The local magnetic properties and electronic structures of Cu 12 R clusters with I h and O h symmetries (RϭSc, Ti, V, Cr, Mn, Fe, Co, Ni, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, and Ag͒ have been systematically studied with the density-functional formalism, and the Kohn-Sham equation is solved self-consistently with the discrete variational method. By calculating the binding energies for 3d series, we find that the icosahedral structure is more stable than the octahedron structure. Pd and Ag doping can enhance the stability of a cluster, and the alloying effects in such doped clusters have an important effect on binding energy. The electronic structures calculated in equilibrium configurations show that the clusters with RϭCu, Cr, Mo, or Ag have closed electronic shells, while the others have open electronic shells. In particular, we have performed comprehensive calculations on the local magnetism of impurities in a cluster, and found that the behavior of local magnetism for 3d and 4d impurities in Cu 12 clusters is different from that in bulk as well as from that in Al 12 clusters. In contrast to the d-d interaction picture for local magnetism in the d-band bulk host, we have found that there are more complicated interactions acting in clusters to affect the local magnetism of impurities: the interactions of the Cu-p orbital with R-spd orbitals play a crucial role on the local magnetic moment for impurities with more than a half-filled d shell, such as Mn, Fe, Co, Ni, Tc, Ru, and Rh; the interactions of the Cu-d orbital with R-spd orbitals contribute to the local magnetic moment for impurites with a less than half-filled d shell, such as Sc, Ti, V, Y, Zr, and Nb. We have also tested and discussed the Stoner-like criterion for the occurrence of a local moment in a cluster.

The magic oxide clusters M 9 O 6 (M ϭFe, Co, Ni) are found by using reactive laser vaporized cluster source. From the first-principles calculations, the possible equilibrium geometries for these three oxide clusters are determined to be a C 2v symmetry, where the skeleton composed of 9 metal atoms also has C 2v symmetry, different from the equilibrium structures of pure transition metal cluster M 9 . The O atoms are energetically more favorable to cap the triangle surfaces. In Fe 9 O 6 and Co 9 O 6 clusters, oxygen atoms are antiferromagnetically polarized while ferromagnetically polarized in the Ni 9 O 6 cluster, similar to the case of O atoms adsorbed on the reconstructed Ni͑110͒ surface. The magnetic behaviors are explained from electronic structures.

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Abstract. The local magnetic property, d electronic structure and the charge transfer effect of Fe impurity in A1 clusters have been studied by using a tight-binding model Hamiltonian in the unrestricted Hartree-Fock approximation, which includes intra-atomic and interatomic Coulomb interactions. We have obtained that local magnetic moment of Fe impurity in FeA1N clusters decreases with increasing cluster size and convergences to zero (that of bulk given by Anderson) with N larger than 12, meanwhile, the local magnetic moment for smaller clusters depends on the clusters size and it is a monotonous descent function of cluster size. We have also found that the spin splitting of the localized d states decreases as the cluster size increases, which mainly results from the interaction between the localized electrons of Fe atom and the delocalized electrons of A1 atoms.

Microstructures of potassium hexatitanate (K2Ti6O13) whiskers prepared by calcination of KF and TiO2 mixture were studied through high-resolution electron microscopy. The rod axis of a K2Ti6O13 whisker is along the [010] direction. These whiskers normally have a lamellar structure in their longitudinal direction, and adjacent lamellae usually have the same crystallographic orientation. Each lamella might be further divided into several fine layers with a width on the nanometer scale in the same crystallographic orientation. The whisker can be split in the longitudinal direction along either the boundary between two lamellae or the weak binding crystal plane, such as (100) and (201) planes. The mechanisms for the formation of lamella and layer structures and for the splitting of whiskers are discussed.

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