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41.
Walter M Häkkinen H Lehtovaara L Puska M Enkovaara J Rostgaard C Mortensen JJ 《The Journal of chemical physics》2008,128(24):244101
We present the implementation of the time-dependent density-functional theory both in linear-response and in time-propagation formalisms using the projector augmented-wave method in real-space grids. The two technically very different methods are compared in the linear-response regime where we found perfect agreement in the calculated photoabsorption spectra. We discuss the strengths and weaknesses of the two methods as well as their convergence properties. We demonstrate different applications of the methods by calculating excitation energies and excited state Born-Oppenheimer potential surfaces for a set of atoms and molecules with the linear-response method and by calculating nonlinear emission spectra using the time-propagation method. 相似文献
42.
Räisänen MT Runeberg N Klinga M Nieger M Bolte M Pyykkö P Leskelä M Repo T 《Inorganic chemistry》2007,46(23):9954-9960
High-yield synthesis of gold(I) thionato complexes, bis(pyridine-2-thionato)gold(I) chloride (1) and bis(pyridine-4-thionato)gold(I) chloride (2), are described. According to their solid-state structures, a linear coordination of Au(I), equiplanar coordination of the ligands and two weak gamma-agostic interactions are found in both of these complexes despite of different relative positions of N and S atoms in the pyridinethionato ligands. Density functional theory calculations on 1 and 2 reproduce the observed X-ray structures. Even though the C-H...Au interactions of Au(I) and two pyridine moieties (2.83 and 2.88 A in 1 and 2.86 A in 2) are relatively weak, according to calculations they seem to provide further stabilization for the coordination and orientation of the ligands. In 1 the shortest Au...Au distances of 3.50 A indicate that aurophilic interactions, even though weak, are present in the solid state, whereas in 2 these interactions are absent. 相似文献
43.
Joakim M. Johansen Martti Aho Kari Paakkinen Raili Taipale Helge Egsgaard Jon G. Jakobsen Flemming J. Frandsen Peter Glarborg 《Proceedings of the Combustion Institute》2013,34(2):2363-2372
Studies of the release of critical ash-forming elements from combustion of biomass are typically conducted with small sample masses under well controlled conditions. In biomass combustion on a grate, secondary recapture and release reactions in the fuel-bed may affect the overall release and partitioning of these elements. Earlier work by the authors on the release of K, Cl, and S from a high-chlorine biomass (corn stover) in a lab-scale setup is, in the present work, supplemented with novel results from a bench-scale fixed bed reactor and a 100 kW moving grate pilot facility. The results from the bench-scale reactor indicate that S and K release are not significantly affected by secondary reactions, while Cl is partly recaptured by secondary reactions in the char. A linear increase in K-release was observed from 50% at 906 °C to almost 80 wt.% at 1234 °C when firing only corn stover. A similar release profile was observed for Cl, from 65% to nearly 100%. Complete release of S was achieved at 1234 °C with a linear increase from 70% at 906 °C. Co-combustion of corn stover with low-Cl wood chips served to increase the bed temperature, resulting in complete and close to complete release of Cl and S, respectively. An increase in the relative K-release was observed when increasing the wood chip fraction from 40% to 100% (energy basis). Pilot scale flue gas results indicate that the share of Cl released as HCl decreases towards 0% as the share of wood chips is increased towards 100%. Hence, co-combustion of corn stover with wood chips is expected to decrease the absolute release of KCl due to the lower feedstock quantity of Cl, however, increase the relative release of Cl as KCl. 相似文献
44.
Teisala H Tuominen M Aromaa M Stepien M Mäkelä JM Saarinen JJ Toivakka M Kuusipalo J 《Langmuir : the ACS journal of surfaces and colloids》2012,28(6):3138-3145
Hierarchical roughness is known to effectively reduce the liquid-solid contact area and water droplet adhesion on superhydrophobic surfaces, which can be seen for example in the combination of submicrometer and micrometer scale structures on the lotus leaf. The submicrometer scale fine structures, which are often referred to as nanostructures in the literature, have an important role in the phenomenon of superhydrophobicity and low water droplet adhesion. Although the fine structures are generally termed as nanostructures, their actual dimensions are often at the submicrometer scale of hundreds of nanometers. Here we demonstrate that small nanometric structures can have very different effect on surface wetting compared to the large submicrometer scale structures. Hierarchically rough superhydrophobic TiO(2) nanoparticle surfaces generated by the liquid flame spray (LFS) on board and paper substrates revealed that the nanoscale surface structures have the opposite effect on the droplet adhesion compared to the larger submicrometer and micrometer scale structures. Variation in the hierarchical structure of the nanoparticle surfaces contributed to varying droplet adhesion between the high- and low-adhesive superhydrophobic states. Nanoscale structures did not contribute to superhydrophobicity, and there was no evidence of the formation of the liquid-solid-air composite interface around the nanostructures. Therefore, larger submicrometer and micrometer scale structures were needed to decrease the liquid-solid contact area and to cause the superhydrophobicity. Our study suggests that a drastic wetting transition occurs on superhydrophobic surfaces at the nanometre scale; i.e., the transition between the Cassie-Baxter and Wenzel wetting states will occur as the liquid-solid-air composite interface collapses around nanoscale structures. Consequently, water adheres tightly to the surface by penetrating into the nanostructure. The droplet adhesion mechanism presented in this paper gives valuable insight into a phenomenon of simultaneous superhydrophobicity and high water droplet adhesion and contributes to a more detailed comprehension of superhydrophobicity overall. 相似文献
45.
The brown crystals of [PMePh3]2[Se2Br6] ( 1 ) and red crystals of [PMePh3]2[SeBr6(SeBr2)2] ( 2 ) were obtained when selenium and bromine reacted in the solution of acetonitrile in the presence of methyltriphenylphosphonium bromide. The crystal structures of 1 and 2 has been determined by the X‐ray methods and refined to R = 0.0373 for 2397 reflections and 0.0397 for 3417 reflections, respectively. The salt 1 crystallizes in the monoclinic space group P21/n with the cell dimensions a = 13.202(5) Å, b = 11.954(4) Å, c = 13.418(6) Å, β = 93.08(4)° (193(2)). The crystals of 2 are triclinic, space group with the cell dimensions a = 10.266(3) Å, b = 11.311(3) Å, c = 11.619(2) Å, α = 108.87(2)°, β = 105.72(2)°, γ = 99.40(2)° (193(2) K). In the solid state structure of 1 the dinuclear hexabromo‐diselenate(II) anion is centrosymmetric and consists of two distorted almost square planar SeBr4 units sharing a common edge through two μ‐bridging Br atoms. The terminal SeII–Br bonds are 2.3984(11) and 2.4273(11) Å, whereas the bridging μBr–SeII bonds are 2.7817(11) and 2.9081(12) Å. In the solid state the trinuclear [SeBr6(SeBr2)2]2? anion of 2 is centrosymmetric too and contains a nearly regular [SeBr6] octahedron where the four equatorial bromo ligands each have developed bonds to the SeII atoms of the SeBr2 molecules. The contacts between the bridging bromo and the SeII atoms of the SeBr2 molecules are 3.0603(15) and 3.1043(12) Å, and can be interpreted as bonds of the donor‐acceptor type with the bridging bromo ligands as donors and the SeBr2 molecules as acceptors. The SeIV–Br distances are in the range 2.5570(9)–2.5773(11) Å and the SeII–Br bond lengths in coordinated SeBr2 molecules – 2.3411(12) and 2.3421(10) Å. 相似文献
46.
In the supersymmetric standard model of particle interactions, R-parity nonconservation is often invoked to obtain nonzero neutrino masses. We point out here that such interactions of the supersymmetric particles would erase any pre-existing lepton or baryon asymmetry of the universe before the electroweak phase transition through the B+L violating sphaleron processes. We also point out that all models of radiative generation of neutrino masses suffer from the same problem. We then show how neutrino masses may be obtained in supersymmetry (assuming R-parity conservation) together with successful leptogenesis and predict the possible existence of new observable particles. 相似文献
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49.
Polarized IR spectra of five benzene derivatives (four of C2v symmetry and one of D2h symmetry) have been recorded using the stretched polymer method. It has been found that the values of the dichroic ratios depend systematically on the symmetry class of the vibration in question. The IR-active vibrations can thus be unambiguously divided into the correct symmetry classes. The general validity of the method, as well as its value for vibrational analysis, is discussed. 相似文献
50.
J. J. Dumont J. Lemonne G. Vanhomwegen F. Verbeure J. H. Wickens V. M. Hagman V. Karimäki J. Tuominiemi K. Valtonen J. A. Estruch W. H. Evans P. Mason H. Muirhead J. F. Baland F. Grard P. Herquet J. Kesteman G. Ekspong B. Selldén L. Szilly N. Yamdagni 《Zeitschrift fur Physik C Particles and Fields》1981,11(2):95-101
A search for directly produced electrons in 70 GeV/cpp interactions has been performed using BEBC equipped with a hydrogen filled track sensitive target surrounded by a hydrogen/neon blanket. No candidates for single electron production with momentump e >500 MeV/c were found in a sample of 66,000 primary interactions. This result places an upper limit of 2.5 μb on the cross section for singlee ± production at the 90% confidence level. The corresponding upper limit on the charmed particle production cross section in 14 μb. From the observation of 7 events producing ane +e? pair with mass, \(m_{e^ + e^ - } > m_{\pi ^0 } \) thee ±/π± ratio from this source is estimated to be (0.7±0.2)×10?4. 相似文献