Bei der Entnahme von Gasl?sungen

Ohne Zusammenfassung     

Distributed memory parallel implementation of energies and gradients for second-order Møller-Plesset perturbation theory with the resolution-of-the-identity approximation

We present a parallel implementation of second-order M?ller-Plesset perturbation theory with the resolution-of-the-identity approximation (RI-MP2). The implementation is based on a recent improved sequential implementation of RI-MP2 within the Turbomole program package and employs the message passing interface (MPI) standard for communication between distributed memory nodes. The parallel implementation extends the applicability of canonical MP2 to considerably larger systems. Examples are presented for full geometry optimizations with up to 60 atoms and 3300 basis functions and MP2 energy calculations with more than 200 atoms and 7000 basis functions.     

Benchmarking the performance of spin-component scaled CC2 in ground and electronically excited states

A generalization of the spin-component scaling and scaled opposite-spin modifications of second-order M?ller-Plesset perturbation theory to the approximate coupled-cluster singles-and-doubles model CC2 (termed SCS-CC2 and SOS-CC2) is discussed and a preliminary implementation of ground and excited state energies and analytic gradients is reported. The computational results for bond distances, harmonic frequencies, adiabatic and 0-0 excitation energies are compared with experimental results to benchmark their performance. It is found that both variants of the spin-scaling increase the robustness of CC2 against strong correlation effects and lead for this method even to somewhat larger improvements than those observed for second-order M?ller-Plesset perturbation theory. The spin-component scaling also enhances systematically the accuracy of CC2 for 0-0 excitation energies for pi --> pi* and n --> pi* transitions, if geometries are determined at the same level.     

Bridgework ahead! Innovation ecosystems vis-à-vis responsible innovation

Public funding agencies largely support academic research as an effort to stimulate future product commercialization and foster broader societal benefits. Yet, translating research nurtured in academic settings into such outcomes is complex and demands functional interactions between government, academic, and industry, i.e., “triple helix,” organizations within an innovation ecosystem. This article argues that in the spirit of responsible innovation, research funding should build bridges that extend beyond the triple helix stakeholders to connect to peripheral organizations. To support that argument, evidence from agent network analysis gathered from two case studies reveals strong and weak connections, as well as gaps within innovation ecosystems in Switzerland and metropolitan Phoenix, USA. This article offers insights on how innovation ecosystems are aligned or misaligned with responsible innovation.     

Chemical effects of continuous and pulsed ultrasound in aqueous solutions

Molecules dissolved in water can undergo pyrolysis and free radical attack when cavitation is produced by ultrasound. Macromolecules are also degraded in the main chain. The yields of these processes depend on the volatility and hydrophobicity of the solutes and on the nature of the gas in the solution. The effects of 1 MHz (quartz) and 20 kHz (horn) are compared; the yield ratio of oxidation to mechanical degradation is strongly dependent on the cavitation conditions. Chemical effects produced by pulsed ultrasound are also described and compared with effects observed in continuous irradiation experiments.     

Effective potentials for spectator groups in molecular systems I. Potential curves and binding energies

Summary A method for representing inactive groups, i.e. spectator groups, in a molecular system by an effective potential is presented. The matrix elements for the spectator's short-range Hartree-Fock potential is stored in an intermediate AO basis, from which it can be transferred into the user basis for the active part of the molecular system. The longer-range of the potential is transferred via a (distributed) multipole expansion. The method is illustrated for the NH₃·X (X=NH₃, H₂O, HF) complexes: binding energies could be reproduced to within 5% by employing the effective NH₃ potential (whereby the lone pair was included in the active system), the entire NH₃·HF potential curve with a depth of 50 kJ/mol is reproduced within 2 kJ/mol if various intermediate basis sets are chosen. Technical details are discussed; the effective potential can directly be introduced in CI calculations.     

Surface chemistry of luminescent colloidal silicon nanoparticles

Luminescent colloidal silicon particles are obtained by burning silane and slowly etching the product with hydrogen fluoride. Depending on their size, the particles emit red-orange or blue-green light with decay times between 28 micros and <0.1 micros, respectively. The quantum yield of the red luminescence is found to be 35%, i.e., much higher than the 7% previously reported, and the yield of the blue-green luminescence is 18%. The luminescence of the colloidal particles is quenched upon the attack of their surface by free radicals, oxygen-centered radicals being more efficient than carbon-centered ones. It is concluded from the dependence of the luminescence wavelength on the etching time and the dependence of the luminescence lifetime on the wavelength that the mechanism of the photoluminescence undergoes a change with decreasing particle size. The red luminescent particles exhibit amphiphilic properties, such as unusual wetting phenomena. This effect is understood in terms of the existence of few polar groups on the otherwise nonpolar surface of the particles, possibly Si-OH groups, which also act as centers of the red luminescence.