First principles theoretical modeling of the isomer shift of Mossbauer spectra

This dissertation details a new approach developed recently, within which the isomer shift is expressed as the derivative of electronic energy with respect to the nuclear radius, it has the clear advantage that relativistic and electron correlation effects can be directly included in the calculation. With the use of the linear response formalism, the performance of various quantum chemical methods were analysed and reliable parametrization of 57Fe and 119Sn nuclei were obtained, which are detailed in this dissertation. The application of the calculated calibration parameters for the investigation on various iron based systems such as the Prussian blue analogues and recently discovered high temperature superconductors are described in this dissertation.

FENO and polymorphisms in the NOS genes SNP- and haplotype-based association analyses

Koncentrationen av kväveoxid i utandningsluft (FENO) är en biomarkör för inflammation i luftvägarna. Variabiliteten mellan individer i FENO är betydande i den allmänna populationen och faktorer som bidrar till variabiliteten är bl.a. fysiologiska, genetiska samt miljöfaktorer. Syftet med studierna i denna avhandling var att tillämpa metoder inom bioinformatik för att karaktärisera variationen hos de tre kväeoxidsyntasgenerna NOS1; NOS2 och NOS3 genom att använda en metod baserad på s.k. tag-SNPar (markör-varianter med förändring i en DNA bas) samt utvärdera det genetiska bidraget till variation i FENO-nivåer hos vuxna. I delarbete 1 utfördes först analys av sambandet mellan 49 SNPar i de tre NOS generna och FENO, en SNP i taget, i en studie-population av 1733 individer. Baserat på graden av association skapades en lista av rangordnade SNPar som sedan användes i en framåt stegvis regressionsanalys för att identifiera ett mindre antal SNPar med starkast oberoende association. Två SNPar (rs9901734 and rs3729508) i NOS2 och en SNP (rs7830) i NOS3 visade oberoende association med FENO-nivå. Individer med NOS2 SNP rs9901734 hade 5.3% (95% CI, 1.0% – 9.7%) högre FENO-nivåer för varje Gallel, och individer med genotyperna CC eller CT NOS2 för SNP rs3729508 hade 9.4% (95% CI 3.1% – 15.2%) högre FENO-nivåer jämfört med TT genotyp. Individer med GT eller TT genotyp i NOS3 SNP rs7830 hade 5.6% (95%CI, 0.4% – 11.1%) högre FENO-nivåer jämfört med GG genotypen. Effekten av denna SNP var starkare hos individer med astma: 21.9%, 95% CI 4.6% – 42.0%. I delarbete 2 undersöktes sambandet mellan haplotyper i NOS2 genen och FENO hos 5912 individer. Tio SNPar utspridda över hela NOS2 genen valdes ut baserat på tidigare kunskap om association med FENO. Sju haplotyper kunde urskiljas, och dessa representerade 84% av alla haplotyper. En haplotyp ('ACCTT)' var signifikant associerad med lägre FENO-nivåer och tre haplotyper ('ACCTC', 'GGCTC' and 'GGCTT') var signifikant associerade med högre FENO-nivåer jämfört med referens-haplotypen ('ACTCT'), med ett globalt p-värde på 3.8×10-28 för haplotyp-distributionen. Associationen mellan haplotyp 'ACCTT' och FENO varierade med astma-status. Sammanfattningvis tyder resultaten på att NOS2 är den av NOS-generna som har störst inverkan på variabiliteten av FENO hos den friska, vuxna befolkningen, och även spelar en roll hos individer med astma. Dessutom indikerande resultaten att en SNP i NOS3 (rs7830) samt en specifik haplotyp ('ACCTT') i NOS2 bidrog mer till variationen av FENO hos individer med astma. Analysen med haplotyper i NOS2 genen kunde påvisa det NOS2-relaterade bidraget till variationen i FENO starkare än analysen med individuella SNPar. Denna studie understryker också potentialen med att kombinera SNP- och haplotyp-baserade metoder för att identifiera och karaktärisera NOS-genernas bidrag till variation i FENO.LIST OF PAPERS This thesis is based on the following papers, referred to in the text by their Roman numerals. I. Dahgam S, Nyberg F, Modig L, Naluai AT, Olin AC. Single nucleotide polymorphisms in the NOS2 and NOS3 genes are associated with exhaled nitric oxide. J Med Genet 2012;49(3):200-5 II. Dahgam S, Modig L, Naluai AT, Olin AC, Nyberg F. Haplotypes of the inducible nitric oxide synthase (NOS2) gene are strongly associated with exhaled nitric oxide levels in adults. (Manuscript)

Calibration of 119Sn isomer shift using ab initio wave function methods

The isomer shift for the 23.87 keV M1 resonant transition in the 119Sn nucleus is calibrated with the help of ab initio calculations. The calibration constant α(119Sn) obtained from Hartree–Fock (HF) calculations (αHF(119Sn)=(0.081±0.002)a0^−3 mm/s) and from second-order Møller–Plesset (MP2) calculations (αMP2(119Sn)=(0.091±0.002)a0^−3 mm/s) are in good agreement with the previously obtained values. The importance of a proper treatment of electron correlation effects is demonstrated on the basis of a statistical analysis of the results of the calibration. The approach used in the calibration is applied to study the 119Sn isomer shift in CaSnO3 perovskite under pressure. Comparison with the experimental results for the pressure range of 0–36 GPa shows that the current methodology is capable of describing tiny variations of isomer shift with reasonable accuracy.

Theoretical investigation on the presence of different iron sites in RbMn[Fe(CN) 6 ]·H 2 O

The Mössbauer spectra of the high-temperature (HT) and the low-temperature (LT) structure

Calibration of Sn-119 isomer shift using ab initio wave function methods

The isomer shift for the 23.87 keV M1 resonant transition in the Sn-119 nucleus is calibrated with the help of ab initio calculations. The calibration constant alpha(Sn-119) obtained from Hartree-Fock (HF) calculations (alpha(HF)(Sn-119)=(0.081 +/- 0.002)a(0)(-3) mm/s) and from second-order Moller-Plesset (MP2) calculations (alpha(MP2)(Sn-119)=(0.091 +/- 0.002)a(0)(-3) mm/s) are in good agreement with the previously obtained values. The importance of a proper treatment of electron correlation effects is demonstrated on the basis of a statistical analysis of the results of the calibration. The approach used in the calibration is applied to study the Sn-119 isomer shift in CaSnO3 perovskite under pressure. Comparison with the experimental results for the pressure range of 0-36 GPa shows that the current methodology is capable of describing tiny variations of isomer shift with reasonable accuracy

Theoretical investigation on the presence of different iron sites in RbMn[Fe(CN)6]·H2O

The 57Fe electron contact densities and the corresponding Mössbauer isomer shifts of RbMn[Fe(CN)6]·H2O are calculated with the use of ab initio wavefunction methods and double hybrid density functional method. The theoretical analysis of possible origin of the two slightly different signals in the Mössbauer spectra observed at 293 K and 50 K is carried out. The measured differences of 0.083 - 0.105 mm/s between the high-temperature and low-temperature phases can be attributed to the different oxidation states of iron: the iron is in FeIII oxidation state in the high temperature phase and FeII state in the low temperature phase. The smaller isomer shift differences of 0.012 - 0.034 mm/s occurring in both high temperature and low temperature structures can be attributed to different distributions of the RbI ions within the unit cell of RbMn[Fe(CN)6]·H2O.

Temperature-Dependent 1s2p Resonant Inelastic X-ray Scattering of CoO

The temperature-dependent 1s2p resonant inelastic X-ray scattering (RIXS) spectra of CoO have been measured with 0.3 eV overall resolution, and the RIXS planes have been analyzed with multiplet calculations. The analysis of the high-resolution 1s2p RIXS plane allows a more detailed determination of the ground-state electronic structure, as compared to Is X-ray absorption spectroscopy (XAS). The apparent absence of interference effects suggests that the lifetime broadening of the pre-edge states is (significantly) reduced from the edge lifetime broadening. The temperature-dependent RIXS planes are explained as a combination of the ground state and first excited state due to thermal population of the excited state, which are a result of the symmetry distortion, 3d spin orbit coupling, and magnetic exchange interactions. No features due to charge transfer and nonlocal transitions are observed due to the relatively small cobalt oxygen overlap as compared to higher valent systems. The successful determination of the spin state and crystal field parameters using hard X-ray experiments promises to make 1s2p RIXS a useful technique for in situ transition metal oxide studies

Intrinsic deviations in fluorescence yield detected x-ray absorption spectroscopy : the case of the transition metal L-2,L-3 edges

Fluorescence yield (FY) detected x-ray absorption spectra (XAS) of 3d transition metal ions are calculated from the integrated 2p3d resonant x-ray emission spectra. The resulting FY-XAS spectra are compared with the normal XAS spectra corresponding to the absorption cross section and significant deviations between the two spectra are found. This implies that the assumption that the FY-XAS spectrum identifies with the XAS spectrum is disproved. Especially for the early transition metal systems the differences between the FY-XAS and XAS are large, due to the opening of inelastic decay channels from selected x-ray absorption final states. The theoretical calculations show that the difference between FY detection and XAS is largest for the detection in depolarized geometry. The calculations are compared with experimental spectra for oxides and coordination compounds for Fe2+, Co2+ and Ni2+ systems. The implications for the sum rules in XAS and magnetic circular dichroism experiments are discussed