Search results for "clusters"

Classes of Colors and Timbres: A Clustering Approach

2022

Similarities between different sensory dimensions can be addressed considering common “movements” as causes, and emotional responses as effects. An imaginary movement toward the “dark” produces “dark sounds” and “dark colors,” or, toward the “bright,” “brighter colors” and “brighter sounds.” Following this line of research, we draw upon the confluence of mathematics and cognition, extending to colors and timbres the gestural similarity conjecture, a development of the mathematical theory of musical gestures. Visual “gestures” are seen here as paths in the space of colors, compared with paths in the space of orchestral timbres. We present an approach based on clustering algorithm to evaluate…

What Is the Limit of Atom Encapsulation for Icosahedral Carboranes?

2015

The stability of endohedral carboranes X@{1,n-C2B10H12} (X = Li(+), Be(2+); n = 2, 7, 12) and X@{CB11H12(-)} (X = Li(+), Be(2+)) is studied using electronic structure calculations with the B3LYP/6-311+G(d,p) model. Our calculations suggest that all endohedral compounds are local energy minima; for the exohedral complexes X···cage, the global energy minimum always corresponds to the X atom above a triangular face of the icosahedron. In the latter the X atom is furthest apart from the carbon atoms of the cage. As opposite to exohedral {Be(2+)···cage} complexes, no global energy minima were found for exohedral complexes {Li(+)···cage} whereby a carbon atom is present in the triangular face of …

Inside Cover: Poly(polyoxotungstate)s with 20 Nickel Centers: From Nanoclusters to One-Dimensional Chains (Angew. Chem. Int. Ed. 39/2009)

2009

[Ag67(SPhMe2)32(PPh3)8]3+: Synthesis, Total Structure, and Optical Properties of a Large Box-Shaped Silver Nanocluster

2016

Engineering the surface ligands of metal nanoparticles is critical in designing unique arrangements of metal atoms. Here, we report the synthesis and total structure determination of a large box-shaped Ag67 nanocluster (NC) protected by a mixed shell of thiolate (2,4-dimethylbenzenethiolate, SPhMe2) and phosphine (triphenylphosphine, PPh3) ligands. Single crystal X-ray diffraction (SCXRD) and electrospray ionization mass spectrometry (ESI-MS) revealed the cluster formula to be [Ag67(SPhMe2)32(PPh3)8]3+. The crystal structure shows an Ag23 metal core covered by a layer of Ag44S32P8 arranged in the shape of a box. The Ag23 core was formed through an unprecedented centered cuboctahedron, i.e.,…

Synthesis of Cuboctahedral CeO2 Nanoclusters and Their Assembly into Cuboid Nanoparticles by Oriented Attachment

2017

Here, we describe a simple approach to control the oriented attachment process through selective ligand scavenging from the {100} facets of CeO2 nanoclusters. Aggregates of these nanoclusters smaller than 10 nm with controlled shapes and exposed facets were obtained. For the synthesis of the cuboctahedral CeO2 nanoclusters, we developed a solvent-controlled synthesis approach based on a non-hydrolytic sol–gel process and used an ester aminolysis reaction to control ligand scavenging from the {100} facets. First-principle calculations allowed us to understand and interpret, at the atomic level, the effects of shape control on the synthesis. Fine-tuning of the desired morphologies can be achi…

Adsorption and reaction of small molecules on palladium clusters: DFT studies

2007

Theoretical study of a palladium cluster on carbonaceous supports

2006

Ab initio determination of the ionization potentials of DNA and RNA nucleobases

2006

Quantum chemical high level ab initio coupled-cluster and multiconfigurational perturbation methods have been used to compute vertical and adiabatic ionization potentials of the five canonical DNA and RNA nucleobases: uracil, thymine, cytosine, adenine, and guanine. Several states of their cations have been also calculated. The present results represent a systematic compendium of these magnitudes, establishing theoretical reference values at a level not reported before, calibrating computational strategies, and guiding the assignment of the features in the experimental photoelectron spectra. Daniel.Roca@uv.es Mercedes.Rubio@uv.es Manuela.Merchan@uv.es Luis.Serrano@uv.es

Cholesky decomposition-based definition of atomic subsystems in electronic structure calculations

2010

Decomposing the Hartree-Fock one-electron density matrix and a virtual pseudodensity matrix, we obtain an orthogonal set of normalized molecular orbitals with local character to be used in post-Hartree-Fock calculations. The applicability of the procedure is illustrated by calculating CCSD(T) energies and CCSD molecular properties in reduced active spaces. © 2010 American Institute of Physics.

Heterometallic CoII-CoIII-MII alkoxido-bridged heptanuclear motifs (M = Cu, Zn). Syntheses, crystal structures and magnetic properties

2018

Two new alkoxido-bridged heterometallic complexes of formula [CoIICoIII 3CuII 3(dea)6(CH3COO)3](ClO4)0.75(CH3COO)1.25 (1) and [CoII 2CoIII 2ZnII 3(tea)2(piv)6(CH3O)2(OH)2(CH3OH)2]·H2O 2 (H2dea=diethanolamine, H3tea=triethanolamine and Hpiv=pivalic acid) have been assembled using aminoalcohol ligands. The cationic core in 1 possesses a threefold crystallographic axis, and it exhibits a set of three copper(II), one cobalt(II) and three cobalt(III) ions arranged as a hexagon of alternating copper(II) and cobalt(III) ions around the central cobalt(II) ion. Each edge of the hexagon is defined by a double alkoxido bridge, the outer one being bis-monodentate with copper(II)-cobalt(III) pair wherea…