| 1. |
- De Vico, Luca, et al.
(författare)
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Chemiluminescence of 1,2-dioxetane. Reaction mechanism uncovered
- 2007
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 111:32, s. 8013-8019
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Tidskriftsartikel (refereegranskat)abstract
- The thermal decomposition of 1,2-dioxetane and the associated production of chemiluminescent products, model for a wide range of chemiluminescent reactions, has been studied at the multistate multiconfigurational second-order perturbation level of theory. This study is in qualitative and quantitative agreement with experimental observations with respect to the activation energy and the observed increase of triplet and singlet excited products as substituents are added to the parent molecule. The, previously incomplete, reaction mechanism of the chemiluminescence of 1,2-dioxetane is now rationalized and described as mainly due to a particular form of entropic trapping.
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| 2. |
- Gagliardi, L, et al.
(författare)
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The electronic spectrum of the UO2 molecule
- 2005
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 127:1, s. 86-91
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Tidskriftsartikel (refereegranskat)abstract
- The electronic spectrum of the UO2 Molecule has been determined using multiconfigurational wave functions together with the inclusion spin-orbit coupling. The molecule has been found to have a (5fphi)(7s), (3)Phi(2u), ground state. The lowest state of gerade symmetry, H-3(4g), corresponding to the electronic configuration (5f)(2) was found 3330 cm(-1) above the ground state. The computed energy levels and oscillator strengths were used for the assignment of the experimental spectrum in the energy range 17000-19000 and 27000-32000 cm(-1).
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| 3. |
- Krogh, Jesper Wisborg
(författare)
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Development and Implementation of Methods in Theoretical Chemistry
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The method development research in the field of theoretical chemistry is the never ending quest for methods that are faster, gives more accurate results, and expands the possibilities. The work in this thesis is no exception to that statement. Thus a CI routine more suited for calculations on large active spaces was implemented in the RASSCF code of Molcas; a new scheme for localizing multipole moments and polarizabilities were developed and implemented; and a parallel SCF code that provides super linear speed up saw the light of the day. These implementations were largely used throughout the remainder of the work, where the nuclear quadrupole moment of tin and the electronic spectrum of UO2 were determined; the photodissociation of bromoiodomethane was investigated; and the ability of localized properties to reproduce the electrostatic potential was tested.
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| 4. |
- Krogh, Jesper Wisborg, et al.
(författare)
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The prediction of the nuclear quadrupole splitting of Sn-119 Mossbauer spectroscopy data by scalar relativistic DFT calculations
- 2006
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 12:19, s. 5116-5121
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Tidskriftsartikel (refereegranskat)abstract
- The electric field gradient components for the tin nucleus of 34 tin compounds of experimentally known structures and Sn-119 Mossbauer spectroscopy parameters were computed at the scalar relativistic density functional theory level of approximation. The theoretical values of the electric field gradient components were used to determine a quantity, V, which is proportional to the nuclear quadrupole splitting parameter (Delta E). In a subsequent linear regression analysis the effective nuclear quadrupole moment, Q, was evaluated. The value of (11.9 +/- 0.1) fm(2) is a significant improvement over the non-relativistic result of (15.2 +/- 4.4) fm(2) and is in agreement with the experimental value of (10.9 +/- 0.8) fm(2). The average mean square error Delta E-calcd-Delta E-exptl = +/- 0.3 mm s(-1) is a factor of two smaller than in the non-relativistic case. Thus, the approach has a quality which provides accurate support for the structure interpretation by Sn-119 spectroscopy. It was noted that geometry optimization at the relativistic level does not significantly increase the quality of the results compared with non-relativistic optimized structures. The accuracy in the approach called on us to consider the singlet-triplet state nature of the electronic structure of one of the investigated compounds.
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| 5. |
- Liu, Ya-Jun, et al.
(författare)
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Spin-orbit ab initio investigation of the photolysis of bromoiodomethane
- 2006
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Ingår i: ChemPhysChem. - : Wiley. - 1439-7641 .- 1439-4235. ; 7:4, s. 955-963
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Tidskriftsartikel (refereegranskat)abstract
- The photodissociation of bromoiodomethane has been investigated by spin-orbit ab initio calculations. The experimentally observed A- and B-bands and the corresponding photoproducts were assigned by multistate second-order multiconfigurationol perturbation theory in conjunction with spin-orbit interaction through complete active space state interaction potential energy curves, vertical excitation energies, and oscillator strengths of low-lying excited states. The present conclusions with respect to the dissociation process in the B-band are different compared with those of previous studies. The reaction between the iso-CH2,Br-I and iso-CH2I-Br species has also been studied. Finally, a set of stable excited states was identified for both isomers. These species might be of importance in the recombination process that follows the photodissociotion in a solvent.
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| 6. |
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| 7. |
- Söderhjelm, Pär, et al.
(författare)
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Accuracy of distributed multipoles and polarizabilities: Comparison between the LoProp and MpProp models
- 2007
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Ingår i: Journal of Computational Chemistry. - : Wiley. - 1096-987X .- 0192-8651. ; 28:6, s. 1083-1090
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Tidskriftsartikel (refereegranskat)abstract
- Localized multipole moments up to the fifth moment as well as localized dipole polarizabilities are calculated with the MpProp and the newly developed LoProp methods for a total of 20 molecules, predominantly derived from amino acids. A comparison of electrostatic potentials calculated from the multipole expansion obtained by the two methods with ab initio results shows that both methods reproduce the electrostatic interaction with an elementary charge with a mean absolute error of similar to 1.5 kJ/mol at contact distance and less than 0.1 kJ/mol at distances 2 angstrom further out when terms up to the octupole moments are included. The polarizabilities are tested with homogenous electric fields and are-found to have similar accuracy. The MpProp method gives better multipole moments unless diffuse basis sets are used, whereas LoProp gives better polarizabilities. (C) 2007 Wiley Periodicals, Inc.
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| 8. |
- Wierzbowska, M, et al.
(författare)
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Condensation energy of the homogeneous electron gas from density-functional theory for superconductors
- 2005
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 71:1, s. 1-014509
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Tidskriftsartikel (refereegranskat)abstract
- The condensation energy of homogeneous electron gas is calculated within the density-functional theory for superconductors. Purely electronic considerations include the exchange energy exactly and the correlation energy on a level of the random phase approximation. Singlet superconductivity is assumed, and the Coulomb interaction is studied with a model pairing potential at angular momentum up to l=9 and densities 1less than or equal tor(s)less than or equal to10. The homogeneous gas remains nonsuperconducting up to r(s)similar or equal to9. A very weak negative value of the condensation energy has been found for f waves and higher-l pairing at r(s)=10.
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