| 1. |
- Aidas, Kestutis, et al.
(författare)
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The Dalton quantum chemistry program system
- 2014
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Ingår i: WIREs Computational Molecular Science. - : Wiley. - 1759-0876 .- 1759-0884. ; 4:3, s. 269-284
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Tidskriftsartikel (refereegranskat)abstract
- Dalton is a powerful general-purpose program system for the study of molecular electronic structure at the Hartree-Fock, Kohn-Sham, multiconfigurational self-consistent-field, MOller-Plesset, configuration-interaction, and coupled-cluster levels of theory. Apart from the total energy, a wide variety of molecular properties may be calculated using these electronic-structure models. Molecular gradients and Hessians are available for geometry optimizations, molecular dynamics, and vibrational studies, whereas magnetic resonance and optical activity can be studied in a gauge-origin-invariant manner. Frequency-dependent molecular properties can be calculated using linear, quadratic, and cubic response theory. A large number of singlet and triplet perturbation operators are available for the study of one-, two-, and three-photon processes. Environmental effects may be included using various dielectric-medium and quantum-mechanics/molecular-mechanics models. Large molecules may be studied using linear-scaling and massively parallel algorithms. Dalton is distributed at no cost from for a number of UNIX platforms.
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| 2. |
- Altmaier, M., et al.
(författare)
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TALISMAN - A European Commission FP7 project promoting transnational access to large infrastructures for a safe management of actinides
- 2014
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Ingår i: Plutonium Futures: The Science 2014; Las Vegas; United States; 7 September 2014 through 12 September 2014. - 9781510808089 ; , s. 165-166
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Konferensbidrag (refereegranskat)abstract
- TALISMAN is a large international project funded within the European Commission FP7 EURATOM framework. The aim of TALISMAN is to offer transnational access to large infrastructures for a safe management of actinides. Although clearly focusing on R&D activities from European Union member states, TALISMAN is also open to participation from non-EU countries. TALISMAN is coordinated by CEA (contact by stephane.bourg@cea.fr), supported by a Governing Board and the ExCom. Dedicated studies on Pu containing materials are integral part of TALISMAN. Safety issues are of fundamental importance for the acceptance and sustainable application of nuclear energy. Actinides play a central role in the nuclear fuel cycle from mining, fuel fabrication, energy production, up to reprocessing, partitioning and transmutation treatment of used fuel, and finally the management and disposal of radioactive waste. Fundamental understanding of actinide properties and behavior in fuel materials during the separation processes and in geological repositories is an imperative prerequisite to tackle the related safety issues. Unravelling the complexity of the actinide components of used nuclear fuel certainly represents one of the great challenges in nuclear science. To meet the needs of safe and sustainable management of nuclear energy it is essential to maintain a high level of expertise in actinide sciences both on a European and international level. Educating and training the next generation of scientists and engineers who will contribute to developing safe actinide management strategies is a key mission. Because actinides are radioactive elements and handling requires specific safety measures, their study requires advanced tools and facilities that are only available to a limited extent. Only a few academic and research organisations have the capabilities and licenses to work on actinide elements. From a European perspective it is therefore strategic to coordinate the existing actinide infrastructures in Europe and strengthen the community of scientists working on actinides. Within TALISMAN we offer (for positively evaluated scientific research proposals submitted in reply to a specific TALISMAN call) access to the previous ACTINET Pooled Facilities (CEA Atalante and CEA DPC, France; ITU Laboratories & hot-cells, European Commission; KIT-INE laboratories and KIT-INE beamline, Germany; HZDR-IRE & ROBL, Germany; PSI microXAS Beamline, Switzerland) to which two new facilities have been added: NNL Central Lab in the UK and CHALMERS in Sweden. TALISMAN is also open to scientists and research organizations from outside the European Union. TALISMAN leads and coordinates a network of actinide facilities across Europe, but also manages a network between facilities and users to increase the knowledge for a safer management of actinides. TALISMAN also enhances the efforts made to support education and training issues by continuing the former ACTINET Summer School series and travel grant attributions for attending international conferences like the Plutonium Futures series. The TALISMAN project website is regularly updated and offers detailed information on all TALISMAN activities at http://www.talisman-project.eu. This is including contact addresses, TALISMAN newsletters, announcements and description of open and forthcoming calls for transnational user access and indicates several other options to perform actinide research within the TALISMAN context.
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| 3. |
- Jansik, B., et al.
(författare)
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A coupled-cluster study of lanthanum trihalide structures
- 2002
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Ingår i: Journal of the Chemical Society. Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1472-7773 .- 1364-5447. ; :24, s. 4603-4606
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Tidskriftsartikel (refereegranskat)abstract
- Coupled-cluster calculations were carried at the CCSD(T)-level in order to determine the structures and vibrational spectra of the lanthanum trihalides LaF3 and LaCl3. Two different approaches were employed to describe scalar relativistic effects; the quasi-relativistic Effective Core Potential approach and the all-electron Douglas-Kroll approach. We find LaF3 to be of pyramidal structure and LaCl3 to be planar. The obtained vibrational frequencies accord well with experimental measurements except for the v(2) mode. This disagreement is attributed to the intrinsic uncertainty of harmonic frequencies of this fluxional mode as extracted from spectra which were obtained at high temperature and for matrix isolated species.
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| 4. |
- Jansik, B., et al.
(författare)
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Relativistic effects on linear and non-linear polarizabilities of the furan homologues
- 2003
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Ingår i: Journal of Molecular Structure. - : Elsevier BV. - 0166-1280. ; 633:03-feb, s. 237-246
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Tidskriftsartikel (refereegranskat)abstract
- First principles calculations including relativistic effects are carried out for dipole moments, polarizabilities, first- and second-order hyperpolarizabilities for the series of furan homologues XC4H4, X = O, S, Se, Te, at three different levels of theory; time-dependent Dirac-Hartree-Fock (DHF), time-dependent Hartree-Fock with a Douglas-Kroll transformed one-component Hamiltonian, and time-dependent Hartree-Fock using effective-core potentials. By comparison with the corresponding non-relativistic results, the influence of relativistic effects on the properties as well as the accuracy of previously reported calculations on these molecules using effective-core potentials for selenium and tellurium can be addressed. The obtained results indicate that relativistic effects can be described with comparable accuracy at all three employed levels, and that non-scalar effects, which are explicitly treated only at the time-dependent DHF level, are of minor importance. Frequency dispersion and relativity are found to be additive at the single-determinant level. We find that relativistic effects cannot make up for the earlier identified mismatch between theory and experiment for the non-linear polarizabilities of the heavier homologues. A Bishop-Kirtman analysis of vibrational effects indicates that the same can be said about these.
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| 5. |
- Jansik, B., et al.
(författare)
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Relativistic effects on linear and non-linear polarizabilities of the furan homologues
- 2003
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Ingår i: Journal of Molecular Structure. - 0166-1280. ; 633:2-3, s. 237-246
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Tidskriftsartikel (refereegranskat)abstract
- First principles calculations including relativistic effects are carried out for dipole moments, polarizabilities, first- and second-order hyperpolarizabilities for the series of furan homologues XC4H 4, X = O, S, Se, Te, at three different levels of theory, time-dependent Dirac-Hartree-Fock (DHF), time-dependent Hartree-Fock with a Douglas-Kroll transformed one-component Hamiltonian, and time-dependent Hartree-Fock using effective-core potentials. By comparison with the corresponding non-relativistic results, the influence of relativistic effects on the properties as well as the accuracy of previously reported calculations on these molecules using effective-core potentials for selenium and tellurium can be addressed. The obtained results indicate that relativistic effects can be described with comparable accuracy at all three employed levels, and that non-scalar effects, which are explicitly treated only at the time-dependent DHF level, are of minor importance. Frequency dispersion and relativity are found to be additive at the single-determinant level. We find that relativistic effects cannot make up for the earlier identified mismatch between theory and experiment for the non-linear polarizabilities of the heavier homologues. A Bishop-Kirtman analysis of vibrational effects indicates that the same can be said about these. © 2003 Elsevier B.V. All rights reserved.
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| 6. |
- Jansik, B., et al.
(författare)
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Relativistic study of vuv radiation properties from Kr-Xe gas mixtures
- 2003
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 67:4
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Tidskriftsartikel (refereegranskat)abstract
- In an effort to obtain a microscopic understanding of the origin of vuv emission from inert heavy-atom gas mixtures we present results from relativistic calculations of the krypton-xenon spectrum in the 68 000 cm(-1) region. Calculations carried out on the interatomic interaction in the ground and in the low-lying spin-orbit excited states [0(-)(P-3(2)), 0(+)(P-3(1)), 1(P-3(1)), 1(P-3(2)), 2(P-3(1))] of the krypton-xenon dimer are presented. The calculations were executed in a two-step procedure in which the CCSD(T) model for the ground state and the CCSD response theory model for the excited states were used to obtain spin-free potential curves in the first step. A perturbational treatment of the spin-orbit interaction within the atomic mean-field approximation was applied in the next step. Large-core quasirelativistic effective core potentials with richly augmented valence basis sets and midbond functions were used. All calculations were corrected for basis set superposition errors by applying the counterpoise method. For all involved states, spin-orbit perturbed potential energy curves were computed and equilibrium geometries, potential well depths, and local extrema were determined. Vibrational analysis and Franck-Condon factors for the ground and 0(+)(P-3(1)),1(P-3(1)) states were also calculated. The geometry dependence of the electronic dipole transition matrix elements between all involved excited states and the ground state was investigated. Excitation energies and potentials were obtained that are in excellent agreement with results based on fitting to experimental data. Out of some earlier disparate experimental assignments of the character of the excited states of the KrXe complex, the present results adhere most closely to the ones presented by Pibel [J. Chem. Phys. 101, 10 242 (1994)]. Analyzed together with the experimental data, the theoretical results provide a clear picture of the organization of exciplex states and of the origin of strong vuv emission from these states that follows from binary collisions of the heavy inert Kr and Xe atoms.
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| 7. |
- Jansik, B., et al.
(författare)
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Size, order, and dimensional relations for silicon cluster polarizabilities
- 2002
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 106:2, s. 395-399
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Tidskriftsartikel (refereegranskat)abstract
- Response theory calculations in the random phase approximation are applied to linear polarizabilities and second hyperpolarizabilities of 1-, 2-, and 3-dimensional hydrogen-terminated silicon clusters. Successive enlargement of the clusters to embody on the order of 50 silicon atoms plus bond-saturating hydrogen atoms allows for extrapolation to bulk values of individual silicon atom contributions in the 1D and 3D cases. Modern effective core potentials are shown to provide excellent approximations to the all-electron values in all cases; errors for both polarizabilities and hyperpolarizabilities are on the order of 1%. The findings indicate considerable time savings in predictions of the electric polarizability properties of elements beyond the first row atoms.
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| 8. |
- Loboda, O., et al.
(författare)
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Ab initio calculations of zero-field splitting parameters in linear polyacenes
- 2003
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Ingår i: Chemical Physics. - 0301-0104 .- 1873-4421. ; 286:1, s. 127-137
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Tidskriftsartikel (refereegranskat)abstract
- The results of ab initio calculations of zero-field splitting (ZFS) parameters are presented for the linear polyacenes from benzene to pentacene. We show how the electron spin-spin (SS) parameters can be efficiently obtained from restricted high-spin open-shell wave functions (ROHF), and present calculations of these, comparing with the results of a recent multi-configurational self-consistent field approach. The SS parameters are obtained from electron SS coupling strengths evaluated as expectation values over the wave functions and from state-to-state spin-orbit (SO) interactions. The results for the two lowest triplet states of naphthalene demonstrate that excellent values can be obtained even using moderate basis sets in the wave function, indicating that this technique can be used to obtain reliable ZFS parameters of aromatic compounds. Electron correlation is, however, not negligible; by accounting for full pi-electron correlation the ZFS parameters are in considerably better agreement with experiment than the ROHF results. The ROHF method still reproduced the qualitative trend in the polyacene series in which the ZFS parameters are reduced with increasing size of the pi-conjugation. We confirm that the SS coupling contributions completely determine the D and E parameters for the lowest triplet state of the linear polyacenes and that the SO coupling contributions are small. Geometry optimization of the lowest triplet state was found to be fairly significant for the calculated D and E values; these were reduced by about 30% and 40%, respectively, when the geometry was changed from the ground-state singlet to the triplet-excited state optimized geometry, with the latter values being in better agreement with experiment. The present calculations predict that the second triplet state of naphthalene is very unusual, as it has a negative zero-field splitting, implying an altered ordering of the spin sublevels compared to what is common in aromatic systems.
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| 9. |
- Engstrom, Maria, et al.
(författare)
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Density functional theory calculations of electron paramagnetic resonance parameters of a nitroxide spin label in tissue factor and factor VIIa protein complex
- 2002
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207 .- 1089-5647. ; 106:47, s. 12354-12360
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Tidskriftsartikel (refereegranskat)abstract
- The electron paramagnetic resonance (EPR) g and N-14 hyperfine coupling (A) tensors of a nitroxide spin label are calculated with density-functional theory (DFT). The influence on the spin label from nearby amino acids in the extracellular part of tissue factor (sTF) and activated factor VII (FVIIa) protein complex is investigated. For that purpose, the nitroxide unit and six surrounding amino acids within 5 Angstrom are selected on the basis of a molecular mechanics structure of the protein complex. The effects of the surroundings on the EPR parameters of the spin label can be divided into indirect effects caused by the induced structure changes of the spin label and direct effects. The structural changes are larger in the present case. The experimentally measurable hyperfine tensor component perpendicular to the molecular plane of the spin label, A(zz), as well as the g tensor component along the NO direction, g,,, are significant probes of the intramolecular structure of the spin label. This indicates the possibility of relating EPR properties to the geometric structure of radical sites. The direct environmental effects on the g tensor from the surrounding amino acids mainly affect the second-order spin-orbit/orbital Zeeman cross-term contributions from the spin label itself. The direct effects originating elsewhere in the model are small. Neither the g nor A tensors display additivity of the effects of individual amino acids on the final observable. The results underline the feasibility of DFT calculations of the EPR parameters in large molecular systems, such as spin labels and other radicals in proteins.
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| 10. |
- Fromager, E., et al.
(författare)
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Spin-orbit effects in electron transfer in neptunyl(VI)-neptunyl(V) complexes in solution
- 2005
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 109:22, s. 4957-4960
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Tidskriftsartikel (refereegranskat)abstract
- The spin-orbit effects were investigated on the complexes involved in the electron self-exchange between Np(V) and Np(VI) in both the outer-sphere and inner-sphere mechanisms, the latter for binuclear complexes containing hydroxide, fluoride, and carbonate as bridging ligands. Results obtained with the variation-perturbation and the multireference single excitation spin-orbit Cl calculations are compared. Both effects due to different relaxations of spinors within a multiplet (spin-orbit relaxation) and scalar (electrostatic) relaxation effects in the excited states are accounted for in the latter scheme. The results show that the scalar (electrostatic) relaxation is well described by the single-excitation spin-orbit CI, and that spin-orbit relaxation effects are small in the Np complexes, as in the lighter d-transition elements but in contrast to the main group elements.
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