Search results for "ab initio"
showing 10 items of 990 documents
Isotope Shifts of Radium Monofluoride Molecules
2021
Isotope shifts of $^{223-226,228}$Ra$^{19}$F were measured for different vibrational levels in the electronic transition $A^{2}{}{\Pi}_{1/2}\leftarrow X^{2}{}{\Sigma}^{+}$. The observed isotope shifts demonstrate the particularly high sensitivity of radium monofluoride to nuclear size effects, offering a stringent test of models describing the electronic density within the radium nucleus. Ab initio quantum chemical calculations are in excellent agreement with experimental observations. These results highlight some of the unique opportunities that short-lived molecules could offer in nuclear structure and in fundamental symmetry studies.
Impact of many-body correlations on the dynamics of an ion-controlled bosonic Josephson junction
2016
We investigate an atomic ensemble of interacting bosons trapped in a symmetric double well potential in contact with a single tightly trapped ion which has been recently proposed [R. Gerritsma et al., Phys. Rev. Lett. 109, 080402 (2012)] as a source of entanglement between a Bose-Einstein condensate and an ion. Compared to the previous study, the present work aims at performing a detailed and accurate many-body analysis of such combined atomic quantum system by means of the ab-initio multi-configuration time-dependent Hartree method for bosons, which allows to take into account all correlations in the system. The analysis elucidates the importance of quantum correlations in the bosonic ense…
A Study Using X-ray Absorption and Emission Spectroscopy of Dioxygen-Binding Xerogels Incorporating Cyclam Units Complexed with Copper Salts.
2005
X-ray absorption spectroscopy was used to elucidate how hybrid xerogels complexed with CuCl2 could reversibly bind molecular dioxygen. Difference EXAFS analyses at the Cu K-edge suggest that dioxygen could bridge two Cu atoms in a μ-η1:η1 peroxo-like conformation with unequal Cu···O distances. Only the short distance (RCu–O1 = 1.86 ± 0.01 A) was unambiguously determined and looks typical of a CuII site. The Cu···Cu internuclear distances would be rather long: RCu–Cu ≈ 4.0 A (3.9 A) for the oxygenated (oxygen-free) xerogels. Cl K-edge EXAFS spectra revealed the pre-existence in the oxygen-free xerogels of CuI sites with short Cl–Cu bonds (2.11 ± 0.03 A). Pentacoordinate CuII sites with a lon…
Substitutional carbon defects in silicon: A quantum mechanical characterization through the infrared and Raman spectra
2020
EUROfusion Enabling Research Project, Grant/Award Number: ENR‐MFE19.ISSP‐UL‐02; GENCI, Grant/Award Number: 2018‐[A0050810537] (Ph. D'Arco) Access to the HPC resources of CINES/IDRIS/TGCC obtained thanks to the grant 2018-[A0050810537]
Theoretical Simulations on Electric Properties of CNT-Me and GNR-Me Interconnects Using Effective Media Approach
2011
Abstract To overcome disadvantages of nowadays microtechnology, a further miniaturization of electronic devices, high integration level as well as increase of both operation frequencies and power density is required, including the use of adequate materials and innovative chip interconnects. Due to their unique physical properties, especially due to a ballistic (without losses) mechanism of conductivity, carbon nanotubes (CNTs) and graphene nanoribbons (GNRs) attract a permanently growing technological interest, for example, as promising candidates for nanointerconnects in a high-speed electronics.
Ab-Initio Calculations of Oxygen Vacancy in Ga2O3 Crystals
2021
The research has been funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (Grant No. AP08856540). J. Purans and A.I.Popov acknowledge the ERAF project 1.1.1.1/20/A/057 “Functional Ultrawide Bandgap Gallium Oxide and Zinc Gallate Thin Films and Novel Deposition Technologies”. The Institute of Solid State Physics, University of Latvia (Latvia) as the Centre of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD01-2016-2017-Teaming Phase2 under grant agreement No. 739508, project CAMART2.
Excitons in few-layer hexagonal boron nitride: Davydov splitting and surface localization
2018
Hexagonal boron nitride (hBN) has been attracting great attention because of its strong excitonic effects. Taking into account few-layer systems, we investigate theoretically the effects of the number of layers on quasiparticle energies, absorption spectra, and excitonic states, placing particular focus on the Davydov splitting of the lowest bound excitons. We describe how the inter-layer interaction as well as the variation in electronic screening as a function of layer number $N$ affects the electronic and optical properties. Using both \textit{ab initio} simulations and a tight-binding model for an effective Hamiltonian describing the excitons, we characterize in detail the symmetry of t…
The bending triad of the quasi-spherical top molecule SO2F2 in the 550 cm(-1) region
2006
International audience; The analysis of the v(3)/v(7)/v(9) bending triad of SO2F2 has been recently performed with the Watson's Hamiltonian up to octic terms employing 79 rovibrational parameters but including only the first order Coriolis interaction terms, fixed to ab initio values [H. Burger, J. Demaison, F. Hegelund, L. Margules, I. Merke, J. Mol. Struct. 612 (2002) 133-141]. Since SO2F2 is a quasi-spherical top, it can also be considered as derived from the SO42- sulfate ion. We have thus developed a new tensorial formalism in the O(3) > Td > C2v group chain [M. Rotger, V. Boudon, M. Loete, J. Mol. Spectrosc. 216 (2002) 297-307]. This approach allows a systematic development of rovibra…
A study of the atmospherically important reactions between dimethyl selenide (DMSe) and molecular halogens (X2 = Cl2, Br2, and I2) with ab initio cal…
2012
The atmospherically relevant reactions between dimethyl selenide (DMSe) and the molecular halogens (X(2) = Cl(2), Br(2), and I(2)) have been studied with ab initio calculations at the MP2/aug-cc-pVDZ level of theory. Geometry optimization calculations showed that the reactions proceed from the reagents to the products (CH(3)SeCH(2)X + HX) via three minima, a van der Waals adduct (DMSe:X(2)), a covalently bound intermediate (DMSeX(2)), and a product-like complex (CH(3)SeCH(2)X:HX). The computed potential energy surfaces are used to predict what molecular species are likely to be observed in spectroscopic experiments such as gas-phase photoelectron spectroscopy and infrared matrix isolation s…
HXeOBr in a xenon matrix
2011
We report on a new noble-gas molecule HXeOBr prepared in a low-temperature xenon matrix from the HBr and N2O precursors by UV photolysis and thermal annealing. This molecule is assigned with the help of deuteration experiments and ab initio calculations including anharmonic methods. The H−Xe stretching frequency of HXeOBr is observed at 1634 cm−1 , which is larger by 56 cm−1 than the frequency of HXeOH identified previously. The experiments show a higher thermal stability of HXeOBr molecules in a xenon matrix compared to HXeOH. peerReviewed