Theoretical Study on the Compounds NpM2, PuM2, AmM2 (M = Mn, Fe, Ni,Co) and on the System Pu-U

The relativistic spin-polarized density functional theory has been used for the study of electronic and magnetic structure of the compounds NpM{sub 2}, PuM{sub 2} and AmM{sub 2} (M = Mn; Fe;Co;Ni). It has been shown that the peculiarities in their magnetic properties come mainly from the hybridization between 5f-electrons of actinides and 3d-electrons of transition metals. It is interesting, that existence of the local magnetic moments appears to be possible on the atoms, despite the fact that Hill's condition is not satisfied for these compounds of actinides. Besides, the electronic and magnetic structures of PuU have been studied and the comparative analysis of them with another compounds of plutonium and its neighbors in Periodic System: PuNp and PuAm has been performed. It has been found that in all the cases the electronic structure formation is a result of a superposition of spin-orbit and exchange band splitting with some increasing of the role of exchange as we are going to americium. Atoms of plutonium appear to be near the point of equal importance of both interactions

Calculational Study on the Compounds Np3M, Am3M, and on the System Pu-Am

Spin-polarized relativistic density functional theory has been employed for the study of the electronic and magnetic structures for the compounds Np{sub 3}M and Am{sub 3}M (M = Al; Ga; In) and their comparison with plutonium's alloys Pu{sub 3}M has been made. It has been found that of the three actinides (Np, Pu, Am) only plutonium has its FCC structure essentially more stable after alloying with aforementioned elements. Apart from that, the electronic and magnetic structures for the system Pu-Am presented by three different compounds: Pu{sub 3}Am, PuAm, and PuAm{sub 3} have been investigated. Their magnetic structures have been found to be too robust in comparison with the experimental fact that magnetism in Pu-Am system depends strongly on the percentage of the americium in the alloy. One possible explanation consists in the overestimation of the spin splitting and in the disregarding of orbital dependence of the exchange-correlation potential

Ab-Initio Study on Plutonium Compounds Pu3M (M=Al, Ga, In), PuNp and Elemental Neptunium

Using spin-polarized relativistic density functional theory the electronic and magnetic structures for the plutonium compounds Pu{sub 3}M(M = Al; Ga; In) and PuNp have been investigated. For the first group of compounds the enhanced hybridization between Pu 5f and p-states of alloying element, as it has been found in spin-polarized calculations, is believed to be the main reason for the higher formation energies obtained in such kind of studies in comparison with the non-spin-polarized case. Also, comparative analysis of the actinides U, Np, Pu, Am, and Cm has been performed based on their electronic and magnetic structure. Some noticeable difference in the calculated magnetic structure was discovered between the actinide with local magnetic moments (Cm) and the actinides (Pu, Am) in which magnetic moments were found only in the calculations

Comparative Analysis of Monochalcogenides of Actinides

The series of monochalcogenides of actinides NpM, PuM, and AmM (M = S; Se; Te) has been studied with relativistic spin-polarized density functional theory. The electronic and magnetic structure of the compounds has been investigated. It has been shown that the hybridization between 5f-electrons of actinides and p-electrons of S, Se, or Te is practically absent. But there is a transfer of electrons from one element to another. This transfer, apparently, is a cause of a crystal field splitting of the bands, which is superimposed on the spin-orbit splitting. The experimental magnetic properties of the above compounds may be explained in this simple picture, obtained from non-spin-polarized calculations. Accounting for magnetism leads to the excessive spin splitting of the bands and to the disagreement with experimental data. So, present work can be considered as one more evidence, that it is necessary to develop more elaborated theory than DFT for study of magnetism in actinides and their compounds

Spin-density fluctuations and the fluctuation-dissipation theorem in 3d ferromagnetic metals

Spatial and time scales of spin density fluctuations (SDF) were analyzed in 3d ferromagnets using ab initio linear response calculations of complete wavevector and energy dependence of the dynamic spin susceptibility tensor. We demonstrate that SDF are spread continuously over the entire Brillouin zone and while majority of them reside within the 3d bandwidth, a significant amount comes from much higher energies. A validity of the adiabatic approximation in spin dynamics is discussed. The SDF spectrum is shown to have two main constituents: a minor low-energy spin wave contribution and a much larger high-energy component from more localized excitations. Using the fluctuation-dissipation theorem (FDT), the on-site spin correlator (SC) and the related effective fluctuating moment were properly evaluated and their universal dependence on the 3d band population is further discussed

Extending MGS-TES Temperature Retrievals in the Martian Atmosphere up to 90 Km: Retrieval Approach and Results

This paper describes a methodology for performing a temperature retrieval in the Martian atmosphere in the 50-90 km altitude range using spectrally integrated 15 micrometers C02 limb emissions measured by the Thermal Emission Spectrometer (TES), the thermal infrared spectrometer on board the Mars Global Surveyor (MGS). We demonstrate that temperature retrievals from limb observations in the 75-90 km altitude range require accounting for the non-local thermodynamic equilibrium (non-LTE) populations of the C02(v2) vibrational levels. Using the methodology described in the paper, we have retrieved approximately 1200 individual temperature profiles from MGS TES limb observations in the altitude range between 60 and 90 km. 0ur dataset of retrieved temperature profiles is available for download in supplemental materials of this paper. The temperature retrieval uncertainties are mainly caused by radiance noise, and are estimated to be about 2 K at 60 km and below, 4 K at 70 km, 7 K at 80 km, 10 K at 85 km, and 20 K at 90 km. We compare the retrieved profiles to Mars Climate Database temperature profiles and find good qualitative agreement. Quantitatively, our retrieved profiles are in general warmer and demonstrate strong variability with the following values for bias and standard deviations (in brackets) compared to the Martian Year 24 dataset of the Mars Climate Database: 6 (+/-20) K at 60 km, 7.5 (+/-25) K at 65 km, 9 (+/-27) K at 70 km, 9.5 (+/-27) K at 75 km, 10 (+/-28) K at 80 km, 11 (+/-29) K at 85 km, and 11.5 (+/-31) K at 90 km. Possible reasons for the positive temperature bias are discussed. carbon dioxide molecular vibration

Validation of the Global Distribution of CO\u3csub\u3e2\u3c/sub\u3e Volume Mixing Ratio in the Mesosphere and Lower Thermosphere from SABER

The Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on board the Thermosphere Ionosphere Mesosphere Energetics and Dynamics satellite has been measuring the limb radiance in 10 broadband infrared channels over the altitude range from ~ 400 km to the Earth\u27s surface since 2002. The kinetic temperatures and CO2 volume mixing ratios (VMRs) in the mesosphere and lower thermosphere have been simultaneously retrieved using SABER limb radiances at 15 and 4.3 μm under nonlocal thermodynamic equilibrium (non-LTE) conditions. This paper presents results of a validation study of the SABER CO2 VMRs obtained with a two-channel, self-consistent temperature/CO2 retrieval algorithm. Results are based on comparisons with coincident CO2 measurements made by the Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) and simulations using the Specified Dynamics version of the Whole Atmosphere Community Climate Model (SD-WACCM). The SABER CO2 VMRs are in agreement with ACE-FTS observations within reported systematic uncertainties from 65 to 110 km. The annual average SABER CO2 VMR falls off from a well-mixed value above ~80 km. Latitudinal and seasonal variations of CO2 VMRs are substantial. SABER observations and the SD-WACCM simulations are in overall agreement for CO2 seasonal variations, as well as global distributions in the mesosphere and lower thermosphere. Not surprisingly, the CO2 seasonal variation is shown to be driven by the general circulation, converging in the summer polar mesopause region and diverging in the winter polar mesopause region. Key Points Mean SABER CO2 distribution is validated against SD-WACCM and ACE-FTS data SABER and ACE-FTS mean CO2 VMR agree within 5% below 90 km up to 20% at 110 km SD-WACCM and SABER CO2 spatial and seasonal distribution show a good agreement. © 2015. American Geophysical Union

Global Distribution of CO2 VMR in the Mesosphere and Lower Thermosphere and Long-Term Changes Observed by SABER

No abstract availabl

Coligomerization of Styrene and a-Methylstyrene Catalyzed by y Zeolites

It is ascertained that during the interaction of styrene and -methylstyrene in the presence of cation and cation-decationated forms of zeolite Y the activity of zeolite catalysts increases in the following order: NiNaY CaNaY <LaNaY 0,5 NY <La Y <NiHY 0,96 Y. The product of reaction in the presence of cation forms of zeolite (NiNaY, CaNaY, LaNaY) is a mixture of low-molecular (n=2 - 4) and high-molecular oligomers (n=14). Oligomers with the degree of oligomerization 2 - 8 are formed in the presence of other zeolite samples. Zeolites 0,96 Y and NiHY allow to receive gomo - and codimers with selectivity 68-80%. The main product of codimerization is cyclic dimer 1,1 – dimethyl – 3-phenylindane