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Atomic clusters

Leonid P Salamakha, Oksana Sologub, Berthold Stöger, Peter Franz Rogl, Monika Waas, Volodymyr B Kapustianyk, Ernst Bauer
Two borides, ScRu2B3 and Sc2RuB6, were obtained by argon-arc melting of the elements followed by annealing at 800 °C. ScRu2B3 exhibits a new structure type with the space group Cmcm (a = 3.0195(2) Å, b = 15.4056(8) Å, c = 5.4492(3) Å; single crystal X-ray data; RF(2) = 0.0105). Sc2RuB6 adopts the Y2ReB6-type structure (space group Pbam; a = 8.8545(2) Å, b = 11.1620(3) Å, c = 3.4760(1) Å; single crystal X-ray data; RF(2) = 0.0185). ScRu2B3 displays an unusual intergrowth of CeCo3B2- and AlB2-related slabs; a striking feature is a boat configuration of puckered boron hexagons within infinite graphite like boron layers (6(3) nets)...
August 16, 2017: Inorganic Chemistry
Xiaohui Gao, Wei Chen
Atomically precise Pd6(SC12H26)12 nanoclusters were synthesized and investigated as electrocatalysts for the hydrogen and oxygen evolution reactions. The present study shows the high catalytic performances of the Pd6 clusters, the key role of the outer-shell electronic state of the metal core in mediating the catalytic properties and the double-edged function of the protecting ligand in the catalytic reactions.
August 16, 2017: Chemical Communications: Chem Comm
Yen-Ching Ho, Yi-Siang Wang, Sheng D Chao
Modeling fluid cycloalkanes with molecular dynamics simulations has proven to be a very challenging task partly because of lacking a reliable force field based on quantum chemistry calculations. In this paper, we construct an ab initio force field for fluid cyclopropane using the second-order Møller-Plesset perturbation theory. We consider 15 conformers of the cyclopropane dimer for the orientation sampling. Single-point energies at important geometries are calibrated by the coupled cluster with single, double, and perturbative triple excitation method...
August 14, 2017: Journal of Chemical Physics
Kun Bu, Zhen-Zhen Li, Jian-Tao Wang
We identify by ab initio calculations a new simple cubic carbon phase in Pa3¯ symmetry, which has a 48-atom unit cell in all-sp(3) bonding networks, thus termed SC48 carbon. It can be viewed as a crystalline form of C12 clusters or a combined structure of SC24 and BC12 carbon, but it is energetically more stable than the recently reported cubic carbon phases such as BC8, SC24, BC12, and fcc-C12. The structural stability is verified by phonon mode analysis. Electronic band and density of state calculations reveal that SC48 carbon is an insulator with a large direct band gap of 4...
August 14, 2017: Journal of Chemical Physics
Heather E Bailey, Yong-Lei Wang, Michael D Fayer
The orientational dynamics and microscopic liquid structure of a protic ionic liquid, 1-ethylimidazolium bis(trifluoromethylsulfonyl)imide (EhimNTf2), and its aprotic analogue, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EmimNTf2), were studied at various water concentrations using optical heterodyne-detected optical Kerr Effect (OHD-OKE) spectroscopy, linear infrared spectroscopy, and atomistic simulations. The OHD-OKE experiments essentially measure the orientational relaxation of the Ehim+ and Emim+ cations...
August 15, 2017: Journal of Physical Chemistry. B
Dong Die, Ben-Xia Zheng, Xiao-Yu Kuang, Zheng-Quan Zhao, Jian-Jun Guo, Quan Du
The structural, electronic and magnetic properties of Cu₄M (M = Sc-Ni) clusters have been studied by using density functional theory, together with an unbiased CALYPSO structure searching method. Geometry optimizations indicate that M atoms in the ground state Cu₄M clusters favor the most highly coordinated position. The geometry of Cu₄M clusters is similar to that of the Cu₅ cluster. The infrared spectra, Raman spectra and photoelectron spectra are predicted and can be used to identify the ground state in the future...
August 15, 2017: Materials
Giacomo Lovat, Bonnie Choi, Daniel W Paley, Michael L Steigerwald, Latha Venkataraman, Xavier Roy
Fabricating nanoscopic devices capable of manipulating and processing single units of charge is an essential step towards creating functional devices where quantum effects dominate transport characteristics. The archetypal single-electron transistor comprises a small conducting or semiconducting island separated from two metallic reservoirs by insulating barriers. By enabling the transfer of a well-defined number of charge carriers between the island and the reservoirs, such a device may enable discrete single-electron operations...
August 14, 2017: Nature Nanotechnology
Jake D Holmes, Alberto Otero-de-la-Roza, Gino A DiLabio
The ability of atom-centered potential (ACPs) to improve the modeling of water clusters using density-functional methods is explored. Water-specific ACPs were developed using accurate ab initio reference data to correct the deficiencies of the BHandHLYP density functional in the calculation of absolute and relative binding energies of water clusters. In conjunction with aug-cc-pVTZ basis sets and with or without dispersion corrections, it is possible to obtain absolute binding energies for water clusters containing up to 10 H2O molecules to within 0...
August 11, 2017: Journal of Chemical Theory and Computation
Linping Qian, Zhen Wang, Evgeny V Beletskiy, Jingyue Liu, Haroldo J Dos Santos, Tiehu Li, Maria do C Rangel, Mayfair C Kung, Harold H Kung
This corrects the article DOI: 10.1038/ncomms14881.
August 11, 2017: Nature Communications
L V Skripnikov
A precise theoretical study of the electronic structure of heavy atom diatomic molecules is of key importance to interpret the experiments in the search for violation of time-reversal (T) and spatial-parity (P) symmetries of fundamental interactions in terms of the electron electric dipole moment, eEDM, and dimensionless constant, kT,P, characterizing the strength of the T,P-odd pseudoscalar-scalar electron-nucleus neutral current interaction. The ACME collaboration has recently improved limits on these quantities using a beam of ThO molecules in the electronic H(3)Δ1 state [J...
December 7, 2016: Journal of Chemical Physics
Benjamin A Legg, James J De Yoreo
According to classical nucleation theory, nucleation from solution involves the formation of small atomic clusters. Most formulations of classical nucleation use continuum "droplet" approximations to describe the properties of these clusters. However, the discrete atomic nature of very small clusters may cause deviations from these approximations. Here, we present a self-consistent framework for describing the nature of these deviations. We use our framework to investigate the formation of "polycube" atomic clusters on a cubic lattice, for which we have used combinatoric data to calculate the thermodynamic properties of clusters with 17 atoms or less...
December 7, 2016: Journal of Chemical Physics
J Scheck, M Drechsler, X Ma, M T Stöckl, J Konsek, J B Schwaderer, S M Stadler, J J De Yoreo, D Gebauer
The interplay between polymers and inorganic minerals during the formation of solids is crucial for biomineralization and bio-inspired materials, and advanced material properties can be achieved with organic-inorganic composites. By studying the reaction mechanisms, basic questions on organic-inorganic interactions and their role during material formation can be answered, enabling more target-oriented strategies in future synthetic approaches. Here, we present a comprehensive study on the hydrolysis of iron(iii) in the presence of polyaspartic acid...
December 7, 2016: Journal of Chemical Physics
Jacek Kłos, Michał Hapka, Grzegorz Chałasiński, Philippe Halvick, Thierry Stoecklin
We present a theoretical study of the Zeeman relaxation of the magnetically trappable lowest field seeking state of CrH(X(6)Σ(+)) in collisions with (3)He. A two dimensional potential energy surface (PES) was calculated with the partially spin-restricted coupled cluster singles, doubles, and non-iterative triples [RCCSD(T)] method. The global minimum was found for the collinear He⋯Cr-H geometry with the well depth of 1143.84 cm(-1) at Re = 4.15 a0. Since the RCCSD(T) calculations revealed a multireference character in the region of the global minimum, we performed additional calculations with the internally contracted multireference configuration interaction with the Davidson correction (ic-MRCISD+Q) method...
December 7, 2016: Journal of Chemical Physics
Ryan L Melvin, Jiajie Xiao, Ryan C Godwin, Kenneth S Berenhaut, Freddie R Salsbury
Correlated motion analysis provides a method for understanding communication between and dynamic similarities of biopolymer residues and domains. The typical equal-time correlation matrices - frequently visualized with pseudo-colorings or heat maps - quickly convey large regions of highly correlated motion but hide more subtle similarities of motion. Here we propose a complementary method for visualizing correlations within proteins (or general biopolymers) that quickly conveys intuition about which residues have a similar dynamic behavior...
August 11, 2017: Protein Science: a Publication of the Protein Society
Meng Zhou, Chenjie Zeng, Matthew Y Sfeir, Mircea Cotlet, Kenji Iida, Katsuyuki Nobusada, Rongchao Jin
Understanding the correlation between the atomic structure and optical properties of gold nanoclusters is essential for exploration of their functionalities and applications involving light harvesting and electron transfer. Here, we report the femto-nanosecond excited state dynamics of a periodic series of face-centered cubic (FCC) gold nanoclusters (including Au28, Au36, Au44, and Au52), which exhibit a set of unique features compared to other similar sized clusters. Molecular-like ultrafast Sn→S1 internal conversions (i...
August 10, 2017: Journal of Physical Chemistry Letters
Peng Shao, Bo-Le Chen, Li Ping Ding, Dao-Bin Luo, Cheng Lu, Xiao-Yu Kuang
New hypervalent molecules have emerged from a systematic exploration of the structure and bonding of MnC (M = Li, Na, K, Rb and Cs; n = 1-8) clusters via an unbiased CALYPSO structure investigation combined with density functional theory. The global minimum structures are obtained at the B3LYP/6-311+G* and CCSD(T)/6-311+G* levels of theory. The observed growth behavior clearly indicates that the ground state of MnC (M = Li, Na, K, Rb and Cs; n = 1-8) is transformed from a planar to a three-dimensional (3D) structure at n = 4...
August 10, 2017: Physical Chemistry Chemical Physics: PCCP
Raisi N Lenz Baldez, Paulo Piquini, Alex A Schmidt, Marcelo A Kuroda
We describe the interaction between small transition metal clusters and graphene using first principles calculations. The coupling is analyzed in terms of different features of the system: binding energy, decomposition into atomic orbitals, the presence of defects on the graphene layer, and both the band and geometrical structures. The binding strength is found to follow the d-band model, which anticipates the binding energies of clusters on graphene layers from the position of the cluster's d-band centers relative to the their highest-occupied and lowest-unoccupied molecular orbital levels...
August 10, 2017: Physical Chemistry Chemical Physics: PCCP
Shao-Peng Pan, Shi-Dong Feng, Jun-Wei Qiao, Xiao-Feng Niu, Wei-Min Wang, Jing-Yu Qin
The breakdown of the Stokes-Einstein relation (SER) in three model metallic liquids is investigated via molecular dynamics simulations. It is found that the breakdown of SER is closely correlated with the clustering behavior of well-packed atoms. When the SER breaks down, many cluster properties have almost the same value in these metallic liquids. At the breakdown temperature of SER, the temperature dependence of the number of clusters begins to deviate from a linear increase and the average number of well-packed atoms in the clusters reaches about 2, which indicates an increase in structure heterogeneity...
August 10, 2017: Physical Chemistry Chemical Physics: PCCP
Robin Guttmann, Alexander F Sax
Weak, intermolecular interactions in amine dimers were studied by using the combination of a dispersionless density functional and a function that describes the dispersion contribution to the interaction energy. The validity of this method was shown by comparison of structural and energetic properties with data obtained with a conventional density functional and the coupled cluster method. The stability of amine dimers was shown to depend on the size, the shape, and the relative orientation of the alkyl substituents, and it was shown that the stabilization energy for large substituents is dominated by dispersion interactions...
August 2017: ChemistryOpen
Manuel Criado
In the adrenal gland, acetylcholine released on stimulation of the sympathetic splanchnic nerve activates neuronal-type nicotinic receptors (nAChRs) in chromaffin cells and triggers catecholamine secretion. At least two subtypes of nAChRs have been described in bovine chromaffin cells. The main subtype, a heteromeric assembly of α3, β4 and perhaps α5 subunits, is involved in the activation step of the catecholamine secretion process and is not blocked by the snake toxin α-bungarotoxin. The other is α-bungarotoxin-sensitive, and its functional role has not yet been well defined...
August 8, 2017: Pflügers Archiv: European Journal of Physiology
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