| 1. |
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| 2. |
- Aryal, M. M., et al.
(författare)
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Understanding of nuclear quadrupole interactions of Cl-35, Br-79 and I-129 and binding energies of solid halogens at first-principles level
- 2007
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Ingår i: Hyperfine Interactions. - : Springer Science and Business Media LLC. - 0304-3843 .- 1572-9540. ; 176:1-3, s. 51-57
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Tidskriftsartikel (refereegranskat)abstract
- This paper deals with the understanding at a first-principles level of the nuclear quadrupole interaction (NQI) parameters of solid chlorine, bromine and iodine as well as the intermolecular binding of these molecules in the solid. The electronic structure investigations that we have carried out to study these properties of the solid halogens are based on the Hartree-Fock Cluster approach using the Roothaan variational procedure with electron correlation effects included using many-body perturbation theory with the empty orbitals used in the perturbation theory investigations for the excited states. The results of our investigations provide good agreement with the measured NQI parameters primarily from the Hartree-Fock one electron wave-functions with many-body effects making minor contributions. The binding (dissociation) energies for the molecules with the solid state environment on the other hand arises from intermolecular many body effects identified as the Van der Waals attraction with one-electron Hartree-Fock contribution being repulsive in nature.
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| 3. |
- Dubey, Archana, et al.
(författare)
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Nuclear quadrupole interactions and electronic structure of BF3 center dot H2O complex
- 2007
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Ingår i: Hyperfine Interactions. - : Springer Science and Business Media LLC. - 0304-3843 .- 1572-9540. ; 176:1-3, s. 45-50
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Tidskriftsartikel (refereegranskat)abstract
- This work deals with first-principles investigation of the electronic structure of the BF3 center dot H2O complex which is important in catalysis of organic reactions and polymerization. The dissociation energy of the BF3 center dot H2O complex and the nuclear quadrupole interaction parameters for the excited nuclear state F-19* (I = 5/2) of the fluorine nuclei have been studied. Our investigation shows that the complexation bond BO between the BF3 and H2O units is strongly influenced by the larger electronegativity of Oxygen as compared to Nitrogen in BF3 center dot NH3. The quadrupole coupling constants of F-19* and the asymmetry parameter are however quite close to those for BF3 center dot NH3. The likely reasons for these features of these two important catalytic systems are suggested.
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| 4. |
- Lata, K. Ramani, et al.
(författare)
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Investigation of the hyperfine properties of deoxy hemoglobin based on its electronic structure obtained by Hartree-Fock-Roothan procedure
- 2008
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Ingår i: Hyperfine Interactions. - : Springer Science and Business Media LLC. - 0304-3843 .- 1572-9540. ; 181:1-3, s. 75-80
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of the heme unit of deoxyhemoglobin including the proximal imidazole has been studied using the first-principles Hartree-Fock procedure. Our results for the Fe-57m isomer shift and asymmetry parameter are in very good agreement with the values obtained from Mossbauer spectroscopy measurements. The Fe-57m nuclear quadrupole coupling constant is smaller than the experimental result and possible ways to improve the agreement in the future are discussed. Improved analysis of the Mossbauer data, removing some approximations made for deriving the magnetic hyperfine tensor for the Fe-57m nucleus, is suggested to allow quantitative comparison with our results in the future.
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| 5. |
- Mahato, Dip N., et al.
(författare)
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First principles study of nuclear quadrupole interactions in the molecular solid BF3 and the nature of binding between the molecules
- 2007
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Ingår i: Hyperfine Interactions. - : Springer Science and Business Media LLC. - 0304-3843 .- 1572-9540. ; 176:1-3, s. 15-20
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structures and nuclear quadrupole interactions (NQI) of the F-19* (I= 5/2) state of F-19 nucleus in solid BF3 are studied using the first-principles Hartree-Fock-Roothaan procedure including many-body electron correlation effects. The calculated NQI parameters, F-19* quadrupole coupling constant (e(2)qQ) and asymmetry parameter eta, were found to be in satisfactory agreement with experiment for the solid state system, which gives confidence in the reliability of the calculated electronic structures in the solid and hence the factors found to influence the binding of the molecules in the solid. It was found that the intermolecular binding energy primarily arises from Van der Waals (VDW) interactions between the molecules resulting from intermolecular many-body effects, which counteract the repulsive interactions between the molecules arising from one-electron Hartree-Fock (HF) theory.
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| 6. |
- Mahato, Dip N., et al.
(författare)
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Theoretical investigation of nuclear quadrupole interactions in DNA at first-principles level
- 2008
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Ingår i: Hyperfine Interactions. - : Springer Science and Business Media LLC. - 0304-3843 .- 1572-9540. ; 181:1-3, s. 81-86
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the nuclear quadrupole interactions (NQI) of the N-14, O-17 and H-2 nuclei in the nucleobases cytosine, adenine, guanine and thymine in the free state as well as when they are bonded to the sugar ring in DNA, simulated through a CH3 group attached to the nucleobases. The nucleobase uracil, which replaces thymine in RNA, has also been studied. Our results show that there are substantial indirect effects of the bonding with the sugar group in the nucleic acids on the NQI parameters e(2)qQ/h and eta. It is hoped that measurements of these NQI parameters in DNA will be available in the future to compare with our predictions. Our results provide the conclusion that for any property dependent on the electronic structures of the nucleic acids, the effects of the bonding between the nucleobases and the nucleic acid backbones have to be included.
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| 7. |
- Pati, Ranjit, et al.
(författare)
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Nuclear Quadrupole Interactions in Nuclear Quadrupole Resonance Detection of Energetic and Controlled Materials : Theoretical Study
- 2012
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Ingår i: Applied Magnetic Resonance. - : Springer Science and Business Media LLC. - 0937-9347 .- 1613-7507. ; 43:4, s. 591-617
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Tidskriftsartikel (refereegranskat)abstract
- There has been a growing interest in nuclear quadrupole resonance (NQR) techniques useful for the detection of explosives and drugs in solid state systems. This paper uses the first-principles one-electron Hartree-Fock theoretical method to study the nuclear quadrupole interaction parameters e (2) qQ and eta for the N-14 nuclei in the explosives RDX and beta-HMX as well as the drugs cocaine and heroin. It has been found in our earlier published investigations reviewed here that there is very good agreement for our calculated e (2) qQ and eta for N-14, for all these four systems, and experiment. We also present our unpublished theoretical results for cocaine with an HCl molecule attached. We successfully explain quantitatively the drastic decrease in e (2) qQ in going to cocaine-HCl from cocaine-free base as well as the observed substantial increase in eta and discuss the implications of these dramatic changes for NQR detection in general.
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| 8. |
- Pink, R. H., et al.
(författare)
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Theory of electronic structure and nuclear quadrupole interactions in the BF3-NH3 complex and methyl derivatives
- 2007
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Ingår i: Hyperfine Interactions. - : Springer Science and Business Media LLC. - 0304-3843 .- 1572-9540. ; 176:1-3, s. 39-44
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic Hyperfine and Nuclear Quadrupole Interactions (HFI and NQI) are now important tools for characterization of systems of interest in materials research and industry. Boron-Trifluoride is an inorganic compound that is very important in this respect as a catalyst in chemical physics research and industry, forming complexes in the process with compounds like ammonia, water and methyl alcohol. The present paper deals with the BF3-NH3 complex and methyl derivatives BF3NHx(CH3)(3-x) for which we have studied the electronic structures, binding energies, and F-19* (I=5/2) nuclear quadrupole interactions using the first-principles Hartree-Fock-Roothaan procedure combined with electron correlation effects. Our results for the F-19* nuclear quadrupole coupling constant (e(2)qQ/h) in units of MHz compare well with experiment. Trends in the binding energies and NQI parameters between the complexes are discussed.
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