| 1. |
- Sharma, S., et al.
(författare)
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First-principles approach to noncollinear magnetism : Towards spin dynamics
- 2007
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 98:19, s. 196405-
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Tidskriftsartikel (refereegranskat)abstract
- A description of noncollinear magnetism in the framework of spin-density functional theory is presented for the exact exchange energy functional which depends explicitly on two-component spinor orbitals. The equations for the effective Kohn-Sham scalar potential and magnetic field are derived within the optimized effective potential (OEP) framework. With the example of a magnetically frustrated Cr monolayer it is shown that the resulting magnetization density exhibits much more noncollinear structure than standard calculations. Furthermore, a time-dependent generalization of the noncollinear OEP method is well suited for an ab initio description of spin dynamics. We also show that the magnetic moments of solids Fe, Co, and Ni are well reproduced.
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| 2. |
- Meis, L. A., et al.
(författare)
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Using reinforcement sensitivity to understand longitudinal links between PTSD and relationship adjustment
- 2017
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Ingår i: Journal of family psychology. - : American Psychological Association. - 0893-3200 .- 1939-1293. ; 31:1, s. 71-81
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Tidskriftsartikel (refereegranskat)abstract
- There is limited research testing longitudinal models of how posttraumatic stress disorder (PTSD) severity leads to impaired relationship adjustment. The present study evaluated 2 potential mechanisms among a longitudinal sample of National Guard soldiers deployed to the Iraq War: (1) sensitivity to cues associated with punishment within intimate relationships and (2) sensitivity to cues associated with incentives in intimate relationships. Participants were surveyed by mail 1 year after an extended 16-month combat deployment and again 2 years later. Using a cross-lagged panel analysis with 2 mediators (relationship-specific threat and incentive sensitivity), findings indicated Time 1 PTSD symptom severity significantly eroded relationship adjustment over time through greater sensitivity to cues of relationship-related punishment, but not through incentive sensitivity. Additionally, findings indicated sensitivity to cues of relationship-related threats maintains symptoms of PTSD while sensitivity to cues of relationship-related incentives maintains relationship adjustment. Finally, PTSD symptoms significantly predicted erosion of relationship adjustment over time; however, associations from relationship adjustment to changes in PTSD severity over time were nonsignificant. Findings are discussed within the context of reinforcement sensitivity theory and emotional processing theory of PTSD.
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| 3. |
- Priestley, Michael, et al.
(författare)
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Chemical characterisation of benzene oxidation products under high- and low-NOx conditions using chemical ionisation mass spectrometry
- 2021
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 21:5, s. 3473-3490
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Tidskriftsartikel (refereegranskat)abstract
- Aromatic hydrocarbons are a class of volatile organic compounds associated with anthropogenic activity and make up a significant fraction of urban volatile organic compound (VOC) emissions that contribute to the formation of secondary organic aerosol (SOA). Benzene is one of the most abundant species emitted from vehicles, biomass burning and industry. An iodide time-of-flight chemical ionisation mass spectrometer (ToF-CIMS) and nitrate ToF-CIMS were deployed at the Julich Plant Atmosphere Chamber as part of a series of experiments examining benzene oxidation by OH under high- and low-NOx conditions, where a range of organic oxidation products were detected. The nitrate scheme detects many oxidation products with high masses, ranging from intermediate volatile organic compounds (IVOCs) to extremely low volatile organic compounds (ELVOCs), including C-12 dimers. In comparison, very few species with C->= 6 and O-> 8 were detected with the iodide scheme, which detected many more IVOCs and semi-volatile organic compounds (SVOCs) but very few ELVOCs and low volatile organic compounds (LVOCs). A total of 132 and 195 CHO
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| 4. |
- Ruban, Andrei V., et al.
(författare)
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Local lattice relaxations in random metallic alloys : Effective tetrahedron model and supercell approach
- 2003
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 67:21
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Tidskriftsartikel (refereegranskat)abstract
- We present a simple effective tetrahedron model for local lattice relaxation effects in random metallic alloys on simple primitive lattices. A comparison with direct ab initio calculations for supercells representing random Ni0.50Pt0.50 and Cu0.25Au0.75 alloys as well as the dilute limit of Au-rich CuAu alloys shows that the model yields a quantitatively accurate description of the relaxtion energies in these systems. Finally, we discuss the bond length distribution in random alloys.
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| 5. |
- Bannan, T. J., et al.
(författare)
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A Large Source of Atomic Chlorine From ClNO2 Photolysis at a UK Landfill Site
- 2019
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Ingår i: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 46:14, s. 8508-8516
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Tidskriftsartikel (refereegranskat)abstract
- Nitryl chloride (ClNO2) acts as a source of highly reactive chlorine atoms as well as an important NOx reservoir. Measurements of ClNO2 at an operational U.K. landfill site are reported here for the first time. A peak concentration of 4 ppb of ClNO2 was found with a peak mean nighttime maximum of 0.9 ppb. Using models based upon the photolysis of observed ClNO2 and atmospheric chlorine chemistry, chlorine atom concentrations reaching in excess of 1.20 x 10(5) molecules/cm(3) in the early morning following sunrise are calculated. These concentrations are approximately 10 times higher than previously reported in the United Kingdom, suggesting a significant impact on the oxidizing capacity around such sites. Given the ubiquity of landfill sites regionally and globally, and the large abundances of Cl atoms from the photolysis of ClNO2, chlorine chemistry has a significant impact on ozone formation and volatile organic compounds oxidation as shown by WRF-Chem modeling. Plain Language Summary Landfill sites are a known source of traces gases into the atmosphere, but measurements often focus predominately on methane and carbon dioxide. A small subsection of trace gas measurements at landfill sites have shown, however, that these sites may be important halogen sources that could have subsequent impacts on air quality and climate. Spatially limited field measurements have previously been reported of a halogen species, ClNO2, showing that this species is consistently formed during nighttime hours, but no such measurements before now have been made at any landfill site. ClNO2 undergoes photolysis upon sunrise, releasing the extremely reactive Cl as well as NO2 into the atmosphere and therefore plays an important part in the total budget and distribution of tropospheric oxidants, halogens, and reactive nitrogen species, all of which are important to air quality. Here we present mass spectrometry measurements of ClNO2 taken at an undisclosed landfill, which show high concentrations in comparison to any other global study of this type. We use predictive modeling techniques to show the importance of this halogen species to air quality, using indicators such as ozone formation. Based on these results we recommend that landfill sources of Cl should be included in future air quality studies.
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| 7. |
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| 8. |
- Le Breton, Michael, 1986, et al.
(författare)
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Chlorine oxidation of VOCs at a semi-rural site in Beijing: significant chlorine liberation from ClNO2 and subsequent gas- and particle-phase Cl-VOC production
- 2018
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 18:17, s. 13013-13030:18, s. 13013-13030
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Tidskriftsartikel (refereegranskat)abstract
- Nitryl chloride (ClNO2) accumulation at night acts as a significant reservoir for active chlorine and impacts the following day's photochemistry when the chlorine atom is liberated at sunrise. Here, we report simultaneous measurements of N2O5 and a suite of inorganic halogens including ClNO2 and reactions of chloride with volatile organic compounds (Cl-VOCs) in the gas and particle phases utilising the Filter Inlet for Gas and AEROsols time-of-flight chemical ionisation mass spectrometer (FIGAERO-ToF-CIMS) during an intensive measurement campaign 40 km northwest of Beijing in May and June 2016. A maximum mixing ratio of 2900 ppt of ClNO2 was observed with a mean campaign nighttime mixing ratio of 487 ppt, appearing to have an anthropogenic source supported by correlation with SO2, CO and benzene, which often persisted at high levels after sunrise until midday. This was attributed to such high mixing ratios persisting after numerous e-folding times of the photolytic lifetime enabling the chlorine atom production to reach 2.3 x 10(5) molecules cm(-3) from ClNO2 alone, peaking at 09:30 LT and up to 8.4 x 10(5) molecules cm(-3) when including the supporting inorganic halogen measurements. Cl-VOCs were observed in the particle and gas phases for the first time at high time resolution and illustrate how the iodide ToF-CIMS can detect unique markers of chlorine atom chemistry in ambient air from both biogenic and anthropogenic sources. Their presence and abundance can be explained via time series of their measured and steady-state calculated precursors, enabling the assessment of competing OH and chlorine atom oxidation via measurements of products from both of these mechanisms and their relative contribution to secondary organic aerosol (SOA) formation.
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| 9. |
- Ruban, Andrei V., et al.
(författare)
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Atomic and magnetic configurational energetics by the generalized perturbation method
- 2004
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 70:12
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Forskningsöversikt (refereegranskat)abstract
- It is shown that, using the generalized perturbation method (GPM) with screened Coulomb interactions that ensures its consistency with the force theorem, one is able to obtain effective interactions that yield an accurate and physically transparent description of configurational energetics in the framework of the Korringa-Kohn-Rostoker method within the atomic sphere and coherent potential approximations. This is demonstrated with calculations of ordering energies, short-range order parameters, and transition temperatures in the CuZn, CuAu, CuPd, and PtCo systems. Furthermore, we show that the GPM can be used to obtain Heisenberg exchange interaction parameters, which, for instance, capture very well the magnetic configurational energy in bcc Fe.
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| 10. |
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