Von den vielen Verfahren zum Nachweis von kleinsten Mengen Formaldehyd

Ohne Zusammenfassung     

Revisiting the extrapolation of correlation energies to complete basis set limit

The extrapolation scheme of correlation energy is revisited to evaluate the complete basis set limit from double‐zeta (DZ) and triple‐zeta levels of calculations. The DZ level results are adjusted to the standard asymptotic behavior with respect to the cardinal number, observed at the higher levels of basis sets. Two types of adjusting schemes with effective scaling factors, which recover errors in extrapolations with the DZ level basis set, are examined. The first scheme scales the cardinal number for the DZ level energy, while the second scheme scales the prefactor of the extrapolation function. Systematic assessments on the Gaussian‐3X and Gaussian‐2 test sets reveal that these calibration schemes successfully and drastically reduce errors without additional computational efforts. © 2015 Wiley Periodicals, Inc.     

Improved description of the orbital relaxation effect by practical use of the self‐energy

The self‐energy shift in the orbital relaxation (OR) term of the polarization propagator complete through the second‐order is presented. In combination with the optimal damping parameter in the OR term, the modified propagator produces the excitation energy of the coupled‐cluster with singles and doubles (CCSD) accuracy. The self‐energy shift requires the floating‐point operation of , where N refers to the magnitude of the molecular size. Because the second‐order polarization propagator requires the floating‐point operation of , the additional computational effort to construct the self‐energy is negligibly small. Numerical results are shown for several molecules including glycine, 2,3,5,6‐tetrafluorobenzene, and naphthalene, and promising agreements with those of CCSD are confirmed within less than 0.2 eV. The basis set dependence is also tested for the water molecule using aug‐cc‐pV NZ (N = D–7), where this newly developed approach mimics the behavior of the CCSD values. The self‐energy shifting for the second‐order response matrix in combination with the use of a dumping parameter is efficiently implemented for calculations of medium‐sized molecular systems, including glycine and naphthalene. The developed approach provides CCSD‐like accuracy at a more affordable computational expense. © 2014 Wiley Periodicals, Inc.     

Confinement in carbon nanospace-induced production of KI nanocrystals of high-pressure phase

An outstanding compression function for materials preparation exhibited by nanospaces of single-walled carbon nanohorns (SWCNHs) was studied using the B1-to-B2 solid phase transition of KI crystals at 1.9 GPa. High-resolution transmission electron microscopy and synchrotron X-ray diffraction examinations provided evidence that KI nanocrystals doped in the nanotube spaces of SWCNHs at pressures below 0.1 MPa had the super-high-pressure B2 phase structure, which is induced at pressures above 1.9 GPa in bulk KI crystals. This finding of the supercompression function of the carbon nanotubular spaces can lead to the development of a new compression-free route to precious materials whose syntheses require the application of high pressure.     

Linearity condition for orbital energies in density functional theory: construction of orbital-specific hybrid functional

This study proposes a novel approach to construct the orbital-specific (OS) hybrid exchange-correlation functional by imposing the linearity condition: ?(2)E/?f(i)(2)|(0≤f(i)≤1) = ??(i)/?f(i)|(0≤f(i)≤1) = 0, where E, ε(i), and f(i) represent the total energy, orbital energy, and occupation number of the ith orbital. The OS hybrid exchange-correlation functional, of which the OS Hartree-Fock exchange (HFx) portion is determined by the linearity condition, reasonably reproduces the ionization potentials not only from valence orbitals but also from core ones in a sense of Koopmans' theorem. The obtained short-range HFx portions are consistent with the parameters empirically determined in core-valence-Rydberg-Becke-3-parameter-Lee-Yang-Parr hybrid functional [Nakata et al., J. Chem. Phys., 124, 094105 (2006); ibid, 125, 064109 (2006)].     

Model study of CO inhibition of [NiFe]hydrogenase

We propose a modified mechanism for the inhibition of [NiFe]hydrogenase ([NiFe]H(2)ase) by CO. We present a model study, using a NiRu H(2)ase mimic, that demonstrates that (i) CO completely inhibits the catalytic cycle of the model compound, (ii) CO prefers to coordinate to the Ru(II) center rather than taking an axial position on the Ni(II) center, and (iii) CO is unable to displace a hydrido ligand from the NiRu center. We combine these studies with a reevaluation of previous studies to propose that, under normal circumstances, CO inhibits [NiFe]H(2)ase by complexing to the Fe(II) center.     

The thermal stabilities of luminescence and microstructures of Eu2+-doped KBaPO4 and NaSrPO4 with β-K2SO4 type structure

Eu(2+)-doped monophosphates NaSrPO(4) and KBaPO(4) with the β-K(2)SO(4) structure were synthesized using the conventional high temperature solid state reaction. The X-ray powder diffraction, photoluminescence excitation, and emission spectra and decay curves were measured. The phosphors can be efficiently excited by UV-visible light from 220 to 430 nm to realize emission in the visible range. The natures of the Eu(2+) emission, e.g., the chromaticity coordinates, the Stokes shifts, and the luminescence absolute quantum efficiencies, were reported. The luminescence quenching temperatures and the thermal activation energies for NaSrPO(4):Eu(2+) and KBaPO(4):Eu(2+) were obtained from the temperature dependent (10-435 K) luminescence intensities and decay curves. KBaPO(4):Eu(2+) presents only one emission center; however, Eu(2+) ions have a "disordered environment" in NaSrPO(4) lattices. The relationship between the luminescence thermal stabilities and the crystal structures was discussed. The crystallographic occupations of rare earth ions doped in these hosts were analyzed by the site-selective emission spectra and the excitation spectra of Eu(3+) ions in the (7)F(0)→(5)D(0) transitions using a pulsed, tunable, and narrow-band dye laser. In KBaPO(4), the Eu(3+) ions could be distributed in the host with a high "ordered state" in only one site in the lattices. However, the multiple site structure of Eu(3+) ions with highly disordered distributions in NaSrPO(4) lattices was suggested.     

Lithium acetylides as alkynylating reagents for the enantioselective alkynylation of ketones catalyzed by lithium binaphtholate

Chiral lithium binaphtholate effectively catalyzed the enantioselective alkynylation of ketones using lithium acetylide as an alkynylating agent. This is the first example of the catalytic enantioselective addition of lithium acetylide to carbonyl compounds without the aid of other metal sources.     

Theoretical reconstruction and elementwise analysis of photoelectron spectra for imidazolium-based ionic liquids

We have recently measured core level and valence band XPS, UPS, and MIES spectra of two room temperature ionic liquids composed of bis(trifluoromethylsulfonyl)imide anions ([Tf(2)N](-)) and either 1-ethyl-3-methyl-imidazolium ([EMIm](+)) or 1-octyl-3-methyl-imidazolium cations ([OMIm](+)). [T. Ikari, A. Keppler, M. Reinm?ller, W. J. D. Beenken, S. Krischok, M. Marschewski, W. Maus-Friedrichs, O. H?fft and F. Endres, e-J. Surf. Sci. Nanotechnol., 2010, 8, 241.] In the present work we analyze these spectra by means of partial density of states (pDOS) as calculated from a single ion pair of the respective ionic liquid using density functional theory (DFT). Subsequently we reconstruct the XPS and UPS spectra by considering photoemission cross sections and analyze the MIES spectra by pDOS, which provides us decisive hints to the ionic liquid surface structure.