Search results for "Calculations"
showing 10 items of 468 documents
Theory of the growth mode for a thin metallic film on an insulating substrate
2002
We have developed a novel theory predicting the growth mode of a thin metallic film on an insulating substrate. This combines ab initio electronic structure calculations for several ordered metal/insulator interfaces (varying both coverage and substrate lattice constant), with a thermodynamic approach based on microscopic calculations. We illustrate this approach for Ag film deposited on MgO(0 0 1) substrate. Ab initio calculations predict high mobility of adsorbed silver atoms on the perfect magnesia surface even at low temperatures. Our theoretical analysis clearly demonstrates that the growth of metallic islands is predominant at the initial stage of silver deposition, which agrees with …
Site symmetry approach applied to the supercell model of MgAl2O4 spinel with oxygen interstitials: Ab initio calculations
2018
This study has been carried out within the framework of the EUROfusion Consortium and has been provided funding from the Euratom research and training programme 2014-2018 under grant agreement No 633053. The authors are indebted to E.A. Kotomin, A.I. Popov and R. Vila for stimulating discussions. The views and opinions expressed herein do not necessarily reflect those of the European Commission. Calculations have been performed using both the Marconi supercomputer system at the Computational Simulation Centre (Italy) and the Computer Center of St. Petersburg State University.
The influence of solvent on conformational properties of peptides with Aib residue—a DFT study
2017
The conformational propensities of the Aib residue on the example of two model peptides Ac-Aib-NHMe (1) and Ac-Aib-NMe2 (2), were studied by B3LYP and M06-2X functionals, in the gas phase and in the polar solvents. To verify the reliability of selected functionals, we also performed MP2 calculations for the tested molecules in vacuum. Polarizable continuum models (PCM and SMD) were used to estimate the solvent effect. Ramachandran maps were calculated to find all energy minima. Noncovalent intramolecular interactions due to hydrogen-bonds and dipole attractions between carbonyl groups are responsible for the relative stabilities of the conformers. In order to verify the theoretical results,…
Reduction of stored-particle background by a magnetic pulse method at the KATRIN experiment
2018
Arenz, M., et al. “Reduction of Stored-Particle Background by a Magnetic Pulse Method at the KATRIN Experiment.” The European Physical Journal C, vol. 78, no. 9, Sept. 2018. © 2018 The Authors
Gamma-induced background in the KATRIN main spectrometer
2019
The KATRIN experiment aims to measure the effective electron antineutrino mass $$m_{\overline{\nu }_e}$$ mν¯e with a sensitivity of $${0.2}\,{\hbox {eV}/\hbox {c}^2}$$ 0.2eV/c2 using a gaseous tritium source combined with the MAC-E filter technique. A low background rate is crucial to achieving the proposed sensitivity, and dedicated measurements have been performed to study possible sources of background electrons. In this work, we test the hypothesis that gamma radiation from external radioactive sources significantly increases the rate of background events created in the main spectrometer (MS) and observed in the focal-plane detector. Using detailed simulations of the gamma flux in the e…
A Computational Study of Two-State Conformational Changes in 16-Electron [CpW(NO)(L)] Complexes (L=PH3, CO, CH2, HCCH, H2CCH2)
1999
International audience; High-spin and low-spin [CpW(NO) (L)] complexes are calculated to be remarkably close in energy. Several critical conformational changes in the singlet compounds are predicted to proceed more readily by spin crossover to the triplet hypersurface. The relationships between spin state, π bonding, ligand orientation, and geometry at W are explored.
Large Conductance Switching in a Single-Molecule Device through Room Temperature Spin-Dependent Transport
2016
Controlling the spin of electrons in nanoscale electronic devices is one of the most promising topics aiming at developing devices with rapid and high density information storage capabilities. The interface magnetism or spinterface resulting from the interaction between a magnetic molecule and a metal surface, or vice versa, has become a key ingredient in creating nanoscale molecular devices with novel functionalities. Here, we present a single-molecule wire that displays large (>10000%) conductance switching by controlling the spin-dependent transport under ambient conditions (room temperature in a liquid cell). The molecular wire is built by trapping individual spin crossover Fe-II comple…
Dicopper(II) metallacyclophanes with photoswitchable oligoacene spacers: a joint experimental and computational study on molecular magnetic photoswit…
2018
Dinuclear copper(II) complexes of the metallacyclophane-type, (nBu4N)4[Cu2(2,6-anba)2] (1) and (nBu4N)4[Cu2(1,5-naba)2]·4H2O (2) with photoactive 2,6-anthracene-(2,6-anba) and 1,5-naphthalenebis(oxamate) (1,5-naba) bridging ligands, are reported. They undergo a thermally reversible, solid-state photomagnetic (ON/OFF) switching between the moderately strong antiferromagnetically coupled dicopper(II) species and the corresponding magnetically uncoupled [4+4] photocycloaddition product. Density functional calculations give further insights on the intramolecular (“pseudo-bimolecular”) photocycloaddition reaction of the two facing 2,6-anthracene or 1,5-naphthalene spacers in this novel family of…
Synthesis and Structural Characterization of Substituted 2-Phenacylbenzoxazoles
2013
1 H and 13C NMR spectra of eleven 2-phenacylbenzoxazoles (ketimine form) show that their CDCl3-solutions contains also (Z)-2-(benzo[d]oxazol-2-yl)-1-phenylethenols (enolimine form). Intramolecular hydrogen bonding in the latter tautomer was found to be significantly weaker than that one in respective (Z)-2-(2-hydroxy-2-phenylvinyl)pyridines. Integrals of the 1 H NMR signals were used to evaluate the molar ratio of the tautomers. Strong electron-donating substituents were found to stabilize the ketimine tautomer. pKT (negative logarithm of the equilibrium constant, KT = [ketimine]/[enolimine]) was found to be linearly dependent on the Hammett substituent constant σ. The results of the MP2 ab…
A Hydrogen-Bonded Supramolecular meso-Helix
2003
[EN] A new one-dimensional hydrogen-bonded polymer with a unique meso-helical structure has been prepared from the spontaneous self-assembly in the solid-state of meta-substituted phenylene dioxamic acid diethyl ester monomers. The helical nature of this molecule and its self-complementary character, through intermolecular hydrogen bonding between oxamic acid ester functions, are the two main factors responsible for the crystalline aggregation process, as confirmed by both experimental X-ray crystallographic data and theoretical ab initio calculations.