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- Hellsvik, Johan, et al.
(författare)
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General method for atomistic spin-lattice dynamics with first-principles accuracy
- 2019
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9969 .- 2469-9950. ; 99:10
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Tidskriftsartikel (refereegranskat)abstract
- We present a computationally efficient and general first-principles based method for spin-lattice simulations for solids and clusters. The method is based on a coupling of atomistic spin dynamics and molecular dynamics simulations, expressed through a spin-lattice Hamiltonian, where the bilinear magnetic term is expanded up to second order in displacement. The effect of first-order spin-lattice coupling on the magnon and phonon dispersion in bcc Fe is reported as an example, and we observe good agreement with previous simulations. We also illustrate the coupled spin-lattice dynamics method on a more conceptual level, by exploring dissipation-free spin and lattice motion of small magnetic clusters (a dimer, trimer, and tetramer). The method discussed here opens the door for a quantitative description and understanding of the microscopic origin of many fundamental phenomena of contemporary interest, such as ultrafast demagnetization, magnetocalorics, and spincaloritronics.
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- Lyngfelt, Anders, 1955, et al.
(författare)
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Dependence of Sulphur Capture Performance on Air Staging in a 12 MW Circulating Fluidised Bed Boiler
- 1993
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Ingår i: Gas Cleaning at High Temperatures, Eds. R. Clift and J.P.K. Seville, Blackie Academic & Professional, Glasgow, ISBN 0 7514 0178 1.. - 0751401781 ; , s. 470-491
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Three cases of air staging were examined in a 12 MW circulating fluidised bed boiler: i) no staging, ii} normal staging and iii) intensified staging. The conditions inside the combustion chamber were investigated by zirconia cell measurements of the oxygen partial pressure, 0.35, 0.65 and 8 m above the bottom air distributor plate. A significant effect of the degree of staging was seen in the two lower locations: At 0.65 m height the fraction of time under substoichiometric conditions was low in the no-staging case (2-35%), at normal staging it was 70-90%, whereas at intensified staging it was 100Y.. At 0.35 m height, i.e. in the dense bed, a similar effect was seen, although the fraction of time under reducing conditions was lower. The fraction of time under reducing conditions was low in the top of the combustion chamber in all three cases . The increase in the fraction of time under reducing conditions with a higher degree of staging is associated with a decrease in sulphur capture. It is assumed that a release of SO2 from CaSO4 takes place during the transitions between oxidising and reducing conditions. Thus, the rapid alternations between oxidising and reducing conditions, as seen with the zirconia cell, offer an explanation of the reductive decomposition and, accordingly, of the dependence of sulphur capture on temperature and on the extent of staging.
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