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81.
Shevlin SA Guo ZX van Dam HJ Sherwood P A Catlow CR Sokol AA Woodley SM 《Physical chemistry chemical physics : PCCP》2008,10(14):1944-1959
Density Functional Theory calculations are reported on cage structured BN, AlN, GaN and InN sub- and low nanosize stoichiometric clusters, including two octahedral families of T(d) and T(h) symmetry. The structures and energetics are determined, and we observe that BN clusters in particular show high stability with respect to the bulk phase. The cluster formation energy is demonstrated to include a constant term that we attribute to the curvature energy and the formation of six tetragonal defects. The (BN)(60) onion double-bubble structure was found to be particularly unstable. In contrast, similar or greater stability was found for double and single shell cages for the other nitrides. The optical absorption spectra have been first characterised by the one-electron Kohn-Sham orbital energies for all compounds, after which we concentrated on BN where we employed a recently developed Time Dependent Density Functional Theory approach. The one-electron band gaps do not show a strong and consistent size dependency, in disagreement with the predictions of quantum confinement theory. The density of excited bound states and absorption spectrum have been calculated for four smallest BN clusters within the first ionisation potential cut-off energy. The relative stability of different BN clusters has been further explored by studying principal point defects and their complexes including topological B-N bond rotational defects, vacancies, antisites and interstititials. The latter have the lowest energy of formation. 相似文献
82.
Cospectral graphs and the generalized adjacency matrix 总被引:1,自引:0,他引:1
Let J be the all-ones matrix, and let A denote the adjacency matrix of a graph. An old result of Johnson and Newman states that if two graphs are cospectral with respect to yJ − A for two distinct values of y, then they are cospectral for all y. Here we will focus on graphs cospectral with respect to yJ − A for exactly one value of y. We call such graphs -cospectral. It follows that is a rational number, and we prove existence of a pair of -cospectral graphs for every rational . In addition, we generate by computer all -cospectral pairs on at most nine vertices. Recently, Chesnokov and the second author constructed pairs of -cospectral graphs for all rational , where one graph is regular and the other one is not. This phenomenon is only possible for the mentioned values of , and by computer we find all such pairs of -cospectral graphs on at most eleven vertices. 相似文献
83.
Chevallier F Halauko YS Pecceu C Nassar IF Dam TU Roisnel T Matulis VE Ivashkevich OA Mongin F 《Organic & biomolecular chemistry》2011,9(12):4671-4684
A series of N-aryl and N-heteroaryl pyrazoles have been deproto-metallated using a 2,2,6,6-tetramethylpiperidino-based mixed lithium-zinc combination. Mono-, di-, and tri-iodides have been obtained after subsequent trapping with iodine, depending on the substrate and on the quantity of base used. The results have been discussed in the light of the CH acidities of the substrates, determined both in the gas phase and in THF solution using the DFT B3LYP method. 相似文献
84.
B Andreasen DM Tanenbaum M Hermenau E Voroshazi MT Lloyd Y Galagan B Zimmernann S Kudret W Maes L Lutsen D Vanderzande U Würfel R Andriessen R Rösch H Hoppe G Teran-Escobar M Lira-Cantu A Rivaton GY Uzunoğlu DS Germack M Hösel HF Dam M Jørgensen SA Gevorgyan MV Madsen E Bundgaard FC Krebs K Norrman 《Physical chemistry chemical physics : PCCP》2012,14(33):11780-11799
The present work is the fourth (and final) contribution to an inter-laboratory collaboration that was planned at the 3rd International Summit on Organic Photovoltaic Stability (ISOS-3). The collaboration involved six laboratories capable of producing seven distinct sets of OPV devices that were degraded under well-defined conditions in accordance with the ISOS-3 protocols. The degradation experiments lasted up to 1830 hours and involved more than 300 cells on more than 100 devices. The devices were analyzed and characterized at different points of their lifetimes by a large number of non-destructive and destructive techniques in order to identify specific degradation mechanisms responsible for the deterioration of the photovoltaic response. Work presented herein involves time-of-flight secondary ion mass spectrometry (TOF-SIMS) in order to study chemical degradation in-plane as well as in-depth in the organic solar cells. Various degradation mechanisms were investigated and correlated with cell performance. For example, photo-oxidation of the active material was quantitatively studied as a function of cell performance. The large variety of cell architectures used (some with and some without encapsulation) enabled valuable comparisons and important conclusions to be drawn on degradation behaviour. This comprehensive investigation of OPV stability has significantly advanced the understanding of degradation behaviour in OPV devices, which is an important step towards large scale application of organic solar cells. 相似文献
85.
Digital microfluidic chips provide a new platform for manipulating chemicals for multi-step chemical synthesis or assays at the microscale. The organic solvents and reagents needed for these applications are often volatile, sensitive to contamination, and wetting, i.e. have contact angles of <90° even on the highly hydrophobic surfaces (e.g., Teflon? or Cytop?) typically used on digital microfluidic chips. Furthermore, often the applications dictate that the processes are performed in a gas environment, not allowing the use of a filler liquid (e.g., oil). These properties pose challenges for delivering controlled volumes of liquid to the chip. An automated, simple, accurate and reliable method of delivering reagents from sealed, off-chip reservoirs is presented here. This platform overcomes the issues of evaporative losses of volatile solvents, cross-contamination, and flooding of the chip by combining a syringe pump, a simple on-chip liquid detector and a robust interface design. The impedance-based liquid detection requires only minimal added hardware to provide a feedback signal to ensure accurate volumes of volatile solvents are introduced to the chip, independent of time delays between dispensing operations. On-demand dispensing of multiple droplets of acetonitrile, a frequently used but difficult to handle solvent due to its wetting properties and volatility, was demonstrated and used to synthesize the positron emission tomography (PET) probe [(18)F]FDG reliably. 相似文献
86.
Christopher John Nuttall Yasuhira Inada Yoshihiro Watanabe Kiyoe Nagai Tsunehiro Muro Dam Hieu Chi 《Molecular Crystals and Liquid Crystals》2013,570(1):635-638
Abstract We report the structural and magnetic properties of the endohedral metallofullerene Ce@C82. A hexagonal close packing phase [P63/mmc [a=11.1544Å, c=18.2256Å] is formed exclusively after vacuum annealing of the solvent precipitated compound. In contrast, sublimed Ce@C82 was found to be dominantly face-centred cubic close packed [Fm-3m; a=15.766Å]. X-ray powder profile calculations revealed that the endohedral cerium atom lies close to 1.8Å from the C82 cage centre in both phases. Hexagonal Ce@C82 has been investigated by magnetic susceptibility measurements. Paramagnetic behaviour is maintained down to 2K attributable to Ce3+ ions. Towards lower temperatures, the observed paramagnetic moment falls from the free ion Ce3+(μeff =2.54μB) value, monotonically approaching 1μB at 2K. 相似文献
87.
We present three models for the extent to which actors reduce their contributions to the production of a public good because of expected contributions by other actors. The first model is a simple game theoretic model, the second a spatial autocorrelation model, and the third is a hybrid of the first two models. Estimation of the three models from incomplete data is discussed. The three models are applied to data on economic policies of municipalities in the Netherlands. In particular, it is probed whether municipalities take a free ride on the measures of their neighbors. 相似文献
88.
D. Allasia C. Angelini A. Baldini L. Bertanza A. Bigi V. Bisi F. Bobisut T. Bolognese A. Borg E. Calimani P. Capiluppi R. Casali S. Ciampolillo R. Cirio J. Derkaoui M. L. Faccini-Turluer V. Flaminio A. G. Frodesen D. Gamba G. Giacomelli H. Huzita B. Iongejans I. Lippi M. Loreti C. Louedec G. Mandrioli A. Margiotta A. Marzari-Chiesa A. Nappi R. Pazzi L. Riccati A. Romero A. M. Rossi A. Sconza P. Serra-Lugaresi A. Tenner G. W. van Apeldoorn P. van Dam N. van Eijndhoven D. Vignaud C. Visser R. Wigmans 《Zeitschrift fur Physik C Particles and Fields》1985,28(3):321-333
89.
Calculated results are reported which indicate the possibility of clustering of interstitial helium in molybdenum. The possible relation of this clustering with surface blistering is discussed. 相似文献
90.
Henk van Dam Jaap N. Louwen Ad Oskam Mark Doran Ian H. Hillier 《Journal of Electron Spectroscopy and Related Phenomena》1980,21(1):57-69
The He(I) and He(II) photoelectron spectra of a series of Fe2(CO)6LL1-type complexes (L = L1 = S, (i-propyl)S; L,L1 = t-but of an all-electron, ab initio SCF MO calculation on Fe2(CO)6S2 and of extended CNDO calculations on related molecules. Assignments given ar He(I)/He(II) intensity differences, and on comparison with related molecules.The coordination of the bridging ligands to the metal centres and the nature of the metal—metal interactions are discussed. 相似文献