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Atomic Species (atomic + species)
Selected AbstractsMolecular Iodine Stabilization in an Extended N···I,I···N AssemblyEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2009Francesco Isaia Abstract The adduct [bis(quinoxaline)-2,2,,3,3,-disulfide·I2], (Q2S2·I2), (1) can be easily synthesised from the reaction of Q2S2 and I2 in CH2Cl2 or, in the absence of any solvent, through diffusion of I2 vapours at 60 °C. X-ray diffraction analysis shows the presence of an extended N···I,I···N assembly in which each I2 molecule links a Q2S2 molecule at both ends through a nitrogen atom to form a polymeric species; the d(I,I) and d(N,I) bond lengths confirm a very weak nitrogen,iodine interaction at the base of the N···I,I···N assembly. DFT calculations provide optimised distances for the N···I and I,I bonds and explanation for the zigzag chain formation: the mPW1PW functional and the B3LYP hybrid functional with a variety of basis sets for the I atomic species [CRENBL, LANL2DZ, LANL2DZ(d,p), LANL08(d), SBKJC, SBKJC polarised-LFK and Stuttgart RLC] have been tested. Compound 1 proved stable up to nearly 100 °C, and the stability is to be mainly attributed to the lattice energy of its polymeric structure then to donor,acceptor stabilisation. The facile insertion of molecular iodine into the Q2S2 network makes this compound an interesting iodine sponge, suitable for I2 storage; moreover, Q2S2 can easily collect and release I2(g) by a temperature-controlled process (60 and 97 °C, respectively). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Application of the Sakurai-Sugiura projection method to core-excited-state calculation by time-dependent density functional theoryJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 14 2008Takashi Tsuchimochi Abstract The Sakurai-Sugiura projection (SS) method was implemented and numerically assessed for diagonalization of the Hamiltonian in time-dependent density functional theory (TDDFT). Since the SS method can be used to specify the range in which the eigenvalues are computed, it may be an efficient tool for use with eigenvalues in a particular range. In this article, the SS method is applied to core excited calculations for which the eigenvalues are located within a particular range, since the eigenvalues are unique to atomic species in molecules. The numerical assessment of formaldehyde molecule by TDDFT with core-valence Becke's three-parameter exchange (B3) plus Lee-Yang-Parr (LYP) correlation (CV-B3LYP) functional demonstrates that the SS method can be used to selectively obtain highly accurate eigenvalues and eigenvectors. Thus, the SS method is a new and powerful alternative for calculating core-excitation energies without high computation costs. © 2008 Wiley Periodicals, Inc. J Comput Chem 2008. [source] Kinetics of coupled ordering and segregation in antiphase domainsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2009K. Gumennyk Abstract We study a multi-domain ordering kinetics in solid solutions under simultaneous diffusion of solute atoms. By the example of a binary bcc alloy a system of kinetic equations is derived, describing the coupled relaxation of occupancies of the two sublattices, building a bcc lattice, by A and B atomic species. Such an approach supplemented by the simplest mean-field approximation proves sufficient to describe both the establishing of long-range order and the segregation processes occurring in antiphase domains. An interaction and interrelation between evolution of the conserved and non-conserved order parameter fields are elucidated. Asymptotical and numerical analysis of the obtained evolution equations reveals a multi-stage scenario of the alloy relaxation: first comes the quick development of long-range order which is then followed by the slow redistribution of local alloy concentration, so that the majority atoms segregate towards the region of an antiphase boundary. The alloy exhibits a distinct tendency to form a multi-domain structure out of a solitary long-range order parameter fluctuation of a certain sign. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Dissecting galaxies with quantitative spectroscopy of the brightest stars in the UniverseASTRONOMISCHE NACHRICHTEN, Issue 5 2010R.-P. KudritzkiArticle first published online: 20 MAY 2010 Abstract Measuring distances to galaxies, determining their chemical composition, investigating the nature of their stellar populations and the absorbing properties of their interstellar medium are fundamental activities in modern extragalactic astronomy helping to understand the evolution of galaxies and the expanding universe. The optically brightest stars in the universe, blue supergiants of spectral A and B, are unique tools for these purposes. With absolute visual magnitudes up to MV , -9.5 they are ideal to obtain accurate quantitative information about galaxies through the powerful modern methods of quantitative stellar spectroscopy. The spectral analysis of individual blue supergiant targets provides invaluable information about chemical abundances and abundance gradients, which is more comprehensive than the one obtained from HII regions, as it includes additional atomic species, and which is also more accurate, since it avoids the systematic uncertainties inherent in the strong line studies usually applied to the HII regions of spiral galaxies beyond the Local Group. Simultaneously, the spectral analysis yields stellar parameters and interstellar extinction for each individual supergiant target, which provides an alternative very accurate way to determine extragalactic distances through a newly developed method, called the Flux-weighted Gravity,Luminosity Relationship (FGLR). With the present generation of 10 m-class telescopes these spectroscopic studies can reach out to distances of 10 Mpc. The new generation of 30 m-class telescopes will allow to extend this work out to 30 Mpc, a substantial volume of the local universe (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||