The 1A1 π→π* state of formaldehyde

The ¹A₁ π→π^* state of formaldehyde is predicted to be 11.2 eV above the ground state and not diffuse.     

Sum-rule moment bounds on long-range van der waals potentials

Quantum-mechanical sum rules and results from the theory of moments are employed in the construction of rigorous bounds on the long range van der Waals interactions of atoms and molecules.     

Lifetime of the He2(e), He2(d) and He2(f) states

Starting from the He₂(a) state absorption and induced fluorescence experiments were performed using a narrow band dye laser. The saturation intensity for the He₂(e)←He₂(a) transition yields a radiative lifetime of τ=(67±10) ns. Time resolved measurements of the laser induced fluorescence yield the radiative lifetimes for the states He₂(e): (57±10) ns, He₂(d): (25±5) ns and He₂(f): (19±5) ns. From the time integrated fluorescence data the collisional quenching rates between the above states were determined.     

Configuration interaction calculations on the nitrogen molecule

A contracted Gaussian basis set capable of describing about 63% of the correlation energy of N₂ has been used in a detailed configuration-interaction calculation. Second-order perturbation theory overestimated the correlation energy by 23–50% depending on how H⁰ was chosen. Pair-pair interaction affects the correlation energy by about 20% while quadruple excitations have an 8% effect.     

A Modulation QCM Applied to Copper Electrodeposition and Stripping

A fast electrochemical quartz crystal microbalance with dissipation monitoring (EQCM−D) was applied to copper electrodeposition and subsequent stripping. Accumulation brings the frequency noise down to the mHz range, corresponding to 0.1 % of a monolayer. With this precision, the apparent mass transfer rate as determined from the time-derivative of the frequency shift can be directly compared to the current. Small but systematic deviations between the two can be attributed to nanoscale roughness. In the voltage range of underpotential deposition (UPD), the apparent mass transfer rate shows peaks and shoulders. The plating additive benzotriazole (BTA) leaves the magnitude of electrogravimetric signals unchanged, but shifts the UPD onset potential. The additive thiourea (TU) promotes UPD and strongly increases the bandwidth.     

Micromechanical estimate of the elastic properties of the coherent domains in pyrolytic carbon

On the nanoscale, the microstructure of pyrolytic carbon (PyC) is constituted by an ensemble of graphene planes, which manifest themselves as lattice fringes in high-resolution transmission electron microscope images. This microstructure can be also considered by an aggregate of so-called coherent domains consisting of stacks of graphene planes with a common unit normal vector. In order to homogenize the elastic behavior of PyC on the micro-level, image processing techniques are used to detect the coherent domains. Subsequently, the domain orientation distribution function (DODF) is modeled by means of a von Mises-Fisher distribution. The main objective of the present paper is to estimate the elastic properties of the coherent domains of the PyC microstructure. Moreover, the Hashin-Shtrikman bounds for the elastic properties can be determined by taking into account the DODF and by applying a nonlinear averaging procedure of the spatially dependent deviations of the local elastic properties. The elastic properties of the coherent domains are estimated by an inverse parameter identification of the Hashin-Shtrikman homogenization method by using effective elastic properties. The latter ones have been obtained based on an Fourier-based image processing algorithm and the orientation distribution function of the graphene planes in a recent paper (Böhlke et al. in Z Angew Math Mech, 2012).     

Homogenization of Linear Elastic Properties of Silicon Nitride

The effective linear elastic properties of silicon nitride (Si₃N₄) are estimated based on first–, third–, and fifth–order bounds of the strain energy density. This specific type of material is a mixture of two linear elastic materials with different material symmetries. The β-Si₃N₄ grains have a hexagonal symmetry with significant amount of anisotropy, whereas the glassy phase is approximately isotropic. The results are as follows: i) The fifth–order upper and lower bounds are almost identical. Therefore, these bounds are sufficient for estimating the effective elastic properties. ii) For fixed elastic constants of the hexagonal β-Si₃N₄ grains, the effective properties of Si₃N₄ are determined as a function of properties of the glassy phase and its volume fraction. The corresponding diagrams allow for the inverse identification of the elastic properties of the glassy phase. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Finite-field calculations of molecular polarizabilities using field-induced polarization functions: second- and third-order perturbation correlation corrections to the coupled Hartree-Fock polarizability of H2O

Ordinary Rayleigh-Schrödinger perturbation theory with Møller-Plesset (RSMP) partitioning is used to calculate second- and third-order correlation corrections to the CHF polarizability and dipole moment of the water molecule by a finite-field procedure. [2/1] Padé approximants are found to be useful in accelerating the convergence of the property perturbation expansions. Field-induced polarization functions suitable for polarizability calculations are determined. The average polarizability calculated, neglecting vibrational averaging, with Dunning's (9s5p/4s-4s2p/2s) contracted GTO basis set augmented by field-induced 1s1p2d/1p polarization functions is within 3 per cent of the experimental result. Correlation corrections to the dipole moment and polarizability of the water molecule calculated by the finite-field RSMP and single + double excitation CI(SDCI) methods for the same basis set are found to be in close agreement. The RSMP approach has the advantages of being size-consistent and of being capable of greater efficiency than the SCDI method. Comparative calculations carried out using Epstein-Nesbet partitioning show that through third order RSEN correlation perturbation expansions for the dipole moment and polarizability are less rapidly convergent than RSMP expansions. However, reasonable accord with RSMP results can be achieved by using [2/1] Padé approximants to accelerate the convergence of RSEN energy perturbation expansions. The convergence of RSMP property correlation expansions based on the zeroth-order uncoupled-Hartree-Fock (UCHF) and coupled-Hartree-Fock (CHF) approximations are compared through third order. Whereas the CHF + RSMP expansions are for practical purposes fully converged, the UCHF + RSMP expansions are not adequately converged.     

Re-entrant corner problems for isotropic materials and layered composites

Modern materials like composites in different types require new methods in computational fracture mechanics. Besides of classical fracture mechanics we have to solve the asymptotic solution around crack tips. This can be done on the basis of the Kondratiev s theorem with the Pietrov-Galerkin method to solve the unknown eigenvalues for those problems. Additionally, we have to de.ne instead classical modes I, II and III, mode I* up to mode IV* to interpret the computational results for the unknown eigenvalues. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)