Studies of new inorganic species using relativistic quantum chemistry

In the present work the methods of relativistic quantum chemistry have been applied to a number of small systems containing heavy elements, for which relativistic effects are important. First, a thorough introduction of the methods used is presented. This includes some of the general methods of computational chemistry and a special section dealing with how to include the effects of relativity in quantum chemical calculations. Second, after this introduction the results obtained are presented. Investigations on high-valent mercury compounds are presented and new ways to synthesise such compounds are proposed. The methods described were applied to certain systems containing short Pt-Tl contacts. It was possible to explain the interesting bonding situation in these compounds. One of the most common actinide compounds, uranium hexafluoride was investigated and a new picture of the bonding was presented. Furthermore the rareness of uranium-cyanide compounds was discussed. In a foray into the chemistry of gold, well known for its strong relativistic effects, investigations on different gold systems were performed. Analogies between Au$^+$ and platinum on one hand and oxygen on the other were found. New systems with multiple bonds to gold were proposed to experimentalists. One of the proposed systems was spectroscopically observed shortly afterwards. A very interesting molecule, which was theoretically predicted a few years ago is WAu$_{12}$. Some of its properties were calculated and the bonding situation was discussed. In a further study on gold compounds it was possible to explain the substitution pattern in bis[phosphane-gold(I)] thiocyanate complexes. This is of some help to experimentalists as the systems could not be crystallised and the structure was therefore unknown. Finally, computations on one of the heaviest elements in the periodic table were performed. Calculation on compounds containing element 110, darmstadtium, showed that it behaves similarly as its lighter homologue platinum. The extreme importance of relativistic effects for these systems was also shown.I detta arbete har relativistiska kvantkemiska metoder tillämpats på ett antal system som innehåller tunga element, för vilka relativistiska effekter är av stor betydelse. I första delen diskuteras de använda metoderna noggrannt. Den teoretiska delen innehåller information om beräkningskemins generella metoder och ett speciellt stycke om hur relativistiska effekter kan inkluderas. Efter den teoretiska delen presenteras resultaten. I en undersökning av högvalenta kvicksilverföreningar föreslås nya möjligheter att syntetisera dem. De teoretiska metoderna tillämpades även på system med korta Pt-Tl bindningar. Den undersökningen förklarar den intressanta bindningen i dessa föreningar. En av de mest använda aktinidföreningarna, uranhexafluorid, studerades också. En ny modell för dess bindningar presenteras. Utöver detta ges en förklaring, varför uran(VI)cyanider är så sällsynta. Guld är välkänt för sina starka relativistiska effekter och därför är guldföreningar en viktig del av detta arbete. Först presenteras flera resultat som visar på en analogi mellan Au+ och syre eller platina och syre. Nya system med multipelbindningar till guld föreslås. Ett av dessa system observerades kort efteråt av experimentalisterna. En mycket intressant molekyl som teoretiskt förutsågs för några år sedan är WAu12. En studie på denna molekyl förklarar den intressanta bindningen mellan Au och W. Även många beräknade fysikaliska egenskaper av WAu12 presenteras. I ett annat arbete undersöktes substitutionsmönstret för olika bis[fosfan-guld(I)]thiocyanatkomplex. Detta arbete är särskilt intressant för experimentalisterna eftersom strukturen av de syntetiserade föreningarna inte var bekannt. Till sist presenteras en undersökning av föreningar av ett av periodiska systemets tyngsta element, darmstadtium (E110, Ds). Beräkningarna visar att Ds beter sig likt sin lättare homolog, platina. De extremt starka relativistiska effekterna syns tydligt i dessa föreningar

Fractional differentiation in the self-affine case I – Random functions

AbstractThe invariance structure of self-affine functions and measures leads to the concept of fractional Cesáro derivatives and densities, respectively. In the present paper the case of random functions from Rp into Rq is considered. It is shown that the corresponding derivatives exist a.s. and equal a constant in the ergodic case. Part II will deal with the class of self-similar extremal processes and certain extensions. In Part III the fractional density of the Cantor measure will be evaluated, and arbitrary self-similar random measures will be treated in Part IV. There exists a deeper connection to fractional differentiation in the theory of function spaces which will be established elsewhere

Responding to Open Access: How German Museums use Digital Content

Museums are expected to safeguard society’s cultural heritage while also making it publicly available to all. Recently, the digital transformation increased political and societal claims on museums to make their digital content openly available. This paper explores museums’ reactions to this claim and looks at how museums currently utilize their digital content. By analysing qualitative interviews with German museum officials we have found museums to follow four different types of strategies which are ‘Societal engagement’, ‘Safeguarding of heritage related knowledge’, ‘Scientific infrastructure’ and ‘marketing ends’. These were embedded in museums’ organizational identity and the prioritising of some of their tasks

Maximizing the Mitigation Potential of Curtailed Wind: A Comparison Between Carbon Capture and Utilization, and Direct Air Capture Processes for the UK

Carbon capture and storage (CCS) with fossil fuel or biomass plants (BECCS) is considered a critical technology to meet mitigation targets set by the Paris Agreement1. However, several drawbacks including high upfront investment costs, significant energy penalty and long-term permanent storage challenges have limited the uptake of CCS on the required scale. Carbon capture and utilisation (CCU) provides an alternative route to recycle CO2 into chemical feedstock and/or synthetic transport fuels (e.g. methanol, DME) that can displace fossil-derived fuels. As the carbon is only transformed, CCU must be integrated with capture/storage to actually offset subsequent emissions from the vehicles consuming them. The mitigation of decentralised emissions poses significant challenges and necessitates the use of carbon dioxide removal technologies (CDR), one of which is direct capture of CO2 from the atmosphere (DAC). The last decade has seen increasing penetration of wind power in the UK electricity system to meet mitigation targets. Because of this, periods of surplus wind generation and low demand or limited/full storage capacity arise. Constraint payments then have to be made to wind farms to curtail generation. This work investigates two possible options to achieve mitigation with this curtailed electricity. In Process A, curtailed electricity is used to produce electrolytic hydrogen and operate methanol synthesis plants. It is then integrated with a direct air capture (DAC) plant to recapture and recycle emissions from the vehicles. Process B assumes curtailed electricity is used to run a DAC plant directly in order to capture decentralised carbon emissions and provide CO2 feedstock for CCU processes. The UK was used as a case study and the methanol synthesis process described by Rihko-Struckmann et al.2 was used as the reference. A range of energy requirements for DAC are cited in literature; the lower and upper bounds of 6.7 GJ/tCO2 and 12.6 GJ/tCO23, respectively, were used. This work has taken a base case curtailment level of 2.5% of the UK total electricity demand, which is equivalent to 390 GWh/y4. Both processes have been compared on the basis of mitigation potential, defined by the proportion of CO2 emissions from gasoline vehicles that are avoided, and mitigation costs per tonne of CO2 captured. Process A resulted in avoiding 0.12% of gasoline emissions (~0.05 MtCO2/y). Surplus energy (~64% of the curtailed electricity) was required to run the DAC plant and an associated air separation unit. The mitigation of potential of Process B was 0.10% or 0.18%, depending on energy requirement used. Therefore, the process that maximises mitigation potential depends on the DAC process considered; using the lower-bound energy requirement, surplus electricity for DAC only is preferable. Neither process is economically viable. CCU costs ($905/tCO2) were found to be double the DAC-only costs ($449/tCO2), mainly due to high H2 costs. It will remain financially-unattractive unless the methanol production becomes profitable. This is unlikely as it requires methanol price to almost double, a carbon price of $313/t to be in effect, or H2 price to reduce to a third of today’s price to$1800/t. References 1. IPCC. Climate Change 2014: Mitigation of Climate Change. Working Group III Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (2014). doi:10.1017/CBO9781107415416 2. Rihko-Struckmann, L. K., Peschel, A., Hanke-Rauschenbach, R. & Sundmacher, K. Assessment of methanol synthesis utilizing exhaust CO2 for chemical storage of electrical energy. Ind. Eng. Chem. Res. 49, 11073–11078 (2010). 3. Socolow, R. et al. Direct Air Capture of CO 2 with Chemicals Panel on Public Affairs. Am. Phys. Soc. - Panel Public Aff. 100 (2011). 4. Messiou, A. Centre for Environmental Policy Investigating the role of power storage in accommodating the future wind. (2012)

Power-to-transport: Using curtailed wind to run CCU processes

The Paris Agreement signaled global commitment to limit average global temperature rise to 2˚C and to make efforts to achieve 1.5˚C increase (UNFCCC, 2015). The IPCC AR5 cites carbon capture and storage (CCS) as a necessary technology to achieve this (IPCC, 2014). However, several drawbacks including high upfront investment costs, significant energy penalty and long-term permanent storage challenges have limited the uptake of CCS on the required scale (Styring, et al., 2011). Carbon capture and utilisation (CCU) provides an alternative route to recycle CO2 into chemical feedstock and/or synthetic transport fuels (e.g. methanol, DME) that can displace fossil-derived fuels. As the carbon is only transformed, CCU must be integrated with capture/storage to actually offset subsequent emissions from the vehicles consuming them. The mitigation of decentralised emissions poses significant challenges and necessitates the use of carbon dioxide removal technologies (CDR), one of which is direct capture of CO2 from the atmosphere (DAC). This work investigates two possible options for CCU integrated with DAC: Option A is the storage of curtailed wind as methanol which can be used in road vehicles to displace gasoline emissions (power-to-transport), and Option B is the use curtailed wind directly to run a DAC plant in order to capture decentralised carbon emissions and provide CO2 feedstock for CCU processes. A high-level analysis has been carried out to determine the gasoline substitution and emissions offset potential of both options, the overall conversion efficiency of the power-to-transport process, and the economics of each option. The UK was used as a case study and the methanol synthesis process described by (Rihko-Struckmann, et al., 2010) was used as the reference. Work by (Messiou, 2012) investigated the curtailment levels for the UK electricity system with increased wind generation; the ‘medium integration’ scenario assumed the UK had 5 times the current wind generation capacity. A corresponding curtailment level of 2.5% (of total electricity dispatched) was determined, this has been used as the base case in our analysis. The gasoline substitution potential of methanol produced via option A was ~0.12% (equivalent to ~0.05 MtCO2/y) with the overall power-to-transport efficiency being ~11%. Surplus energy (~64% of the curtailed electricity) was required to run the DAC plant and an associated air separation unit. The methanol production plant was found to be economically infeasible unless current methanol price increased by a factor of 1.8 to $988/t, the cost of hydrogen fell by a factor of 2.3 to$1811/t or a carbon price of $313/t was in effect. For option B, the emissions offset potential of the DAC process was ~0.18% for the same curtailment, capturing ~0.07 MtCO2/y. Therefore, the utilisation of curtailed electricity for direct capture of CO2 from the atmosphere results in greater avoided emissions than if it was stored as methanol. References IPCC, 2014. Climate Change 2014: Mitigation of Climate Change. Working Group III Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, s.l.: Cambridge University Press. Messiou, A., 2012. Investigating the role of power storage in accommodating the future wind integration into UK’s power system. London: Imperial College London. Rihko-Struckmann, L. K., Peschel, A., Hanke-Rauschenbach, R. & Sundmacher, K., 2010. Assessment of Methanol Synthesis Utilizing Exhaust CO2 for Chemical Storage of Electrical Energy. Industrial and Engineering Chemistry Research, Issue 49, pp. 11073-11078. Styring, P., Jansen, D., de Coninck, H. & Reith, H., 2011. Carbon Capture and Utilisation in the green economy: Using CO2 to manufacture fuel, chemicals and materials, s.l.: The Centre for Low Carbon Futures

Hydrotalcite-derived copper-based oxygen carrier materials for efficient chemical-looping combustion of solid fuels with CO2 capture

Chemical-looping combustion (CLC) is a promising technology that utilizes metal oxides as oxygen carriers for the combustion of fossil fuels to CO2 and H2O, with CO2 readily sequestrated after the condensation of steam. Thermally stable and reactive metal oxides are desirable as oxygen carrier materials for the CLC processes. Here, we report the performance of Cu-based mixed oxides derived from hydrotalcite (also known as layered double hydroxides) precursors as oxygen carriers for the combustion of solid fuels. Two types of CLC processes were demonstrated, including chemical looping oxygen uncoupling (CLOU) and in situ gasification (iG-CLC) in the presence of steam. The Cu-based oxygen carriers showed high performance for the combustion of two solid fuels (a lignite and a bituminous coal), maintaining high thermal stability, fast reaction kinetics, and reversible oxygen release and storage over multiple redox cycles. Slight deactivation and sintering of the oxygen carrier occurred after redox cycles at an very high operation temperature of 985 °C. We expect that our material design strategy will inspire the development of better oxygen carrier materials for a variety of chemical looping processes for the clean conversion of fossil fuels with efficient CO2 capture

Insights into the Electronic Structure of a U(IV) Amido and U(V) Imido Complex

Reaction of the N-heterocylic carbene ligand $^{i}$PrIm (L$^{1}$) and lithium bis(trimethylsilyl)amide (TMSA) as a base with UCl$_{4}$ resulted in U(IV) and U(V) complexes. Uranium\u27s +V oxidation state in (HL$^{1}$)$_{2}$[U(V)(TMSI)Cl$_{5}$] (TMSI=trimethylsilylimido) (2) was confirmed by HERFD-XANES measurements. Solid state characterization by SC-XRD and geometry optimisation of [U(IV)(L$^{1}$)$_{2}$(TMSA)Cl$_{3}$] (1) indicated a silylamido ligand mediated inverse trans influence (ITI). The ITI was examined regarding different metal oxidation states and was compared to transition metal analogues by theoretical calculations

Fractional differentiability of nowhere differentiable functions and dimensions

Weierstrass's everywhere continuous but nowhere differentiable function is shown to be locally continuously fractionally differentiable everywhere for all orders below the `critical order' 2-s and not so for orders between 2-s and 1, where s, 1<s<2 is the box dimension of the graph of the function. This observation is consolidated in the general result showing a direct connection between local fractional differentiability and the box dimension/ local Holder exponent. Levy index for one dimensional Levy flights is shown to be the critical order of its characteristic function. Local fractional derivatives of multifractal signals (non-random functions) are shown to provide the local Holder exponent. It is argued that Local fractional derivatives provide a powerful tool to analyze pointwise behavior of irregular signals.Comment: minor changes, 19 pages, Late

Unwilling U-U bonding in U-2@C-80: cage-driven metal-metal bonds in di-uranium fullerenes

Endohedral actinide fullerenes are rare and a little is known about their molecular properties. Here we characterize the U2@C80 system, which was recently detected experimentally by means of mass spectrometry (Akiyama et al., JACS, 2001, 123, 181). Theoretical calculations predict a stable endohedral system, 7U2@C80, derived from the C80:7 IPR fullerene cage, with six unpaired electrons. Bonding analysis reveals a double ferromagnetic (one-electron-two-center) U-U bond at an rU-U distance of 3.9 Å. This bonding is realized mainly via U(5f) orbitals. The U-U interaction inside the cage is estimated to be about -18 kcal mol-1. U-U bonding is further studied along the U2@Cn (n = 60, 70, 80, 84, 90) series and the U-U bonds are also identified in U2@C70 and U2@C84 systems at rU-U ∼ 4 Å. It is found that the character of U-U bonding depends on the U-U distance, which is dictated by the cage type. A concept of unwilling metal-metal bonding is suggested: uranium atoms are strongly bound to the cage and carry a positive charge. Pushing the U(5f) electron density into the U-U bonding region reduces electrostatic repulsion between enclosed atoms, thus forcing U-U bonds. This journal is © the Owner Societies 2015.Czech Science Foundation [14-03564S]; Czech Academy of Sciences [RVO-61388963]; SoMoPro II program; People Program (Marie Curie action) of the Seventh Framework Program of EU [291782]; South-Moravian Region; European Regional Development Fund [CZ.1.05/1.1.00/02.0068

Holder exponents of irregular signals and local fractional derivatives

It has been recognized recently that fractional calculus is useful for handling scaling structures and processes. We begin this survey by pointing out the relevance of the subject to physical situations. Then the essential definitions and formulae from fractional calculus are summarized and their immediate use in the study of scaling in physical systems is given. This is followed by a brief summary of classical results. The main theme of the review rests on the notion of local fractional derivatives. There is a direct connection between local fractional differentiability properties and the dimensions/ local Holder exponents of nowhere differentiable functions. It is argued that local fractional derivatives provide a powerful tool to analyse the pointwise behaviour of irregular signals and functions.Comment: 20 pages, Late