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11. The influence of the local environment on the electron accepting ability of the cation: induced Lewis acidity

Author

null Tsyganenko A. A, null Shergin Ya. V., null Krauklis I. V., null Rudakova A. V., and null Ezdakova (Voronina) K. V.

Abstract

The effect of adsorption of acid gases CO2, SO2 and SO3 on the electron accepting ability of cations on the surface of calcium oxide was studied by low-temperature IR spectroscopy of adsorbed CO. It is shown that the formation of carbonate, sulfite and sulfate anions in the surface layer leads to the appearance of Lewis acid sites, the strength of which, estimated by the shift in the vibration frequency of CO molecules associated with them, increases in the appropriate order, approaching that for calcium-containing zeolites. The results of the calculation of cluster models by the DFT method confirm the observed trends in the variation of the vibrational frequency and the absorption coefficient of CO molecules bound through both the carbon and oxygen atoms, and also demonstrate the dependence of the ability of a cation for CO linkage isomerism on its local environment. Keywords: surface, adsorption, acidity, IR spectroscopy, quantum chemical calculation, electron accepting ability.

Published
2022
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16. Coordinated ground-based, low altitude satellite and Cluster observations on global and local scales during a transient post-noon sector excursion of the magnetospheric cusp

Author

Opgenoorth, H. J., Lockwood, M., Alcaydé, D., Donovan, E., Engebretson, M. J., van Eyken, A. P., Kauristie, K., Lester, M., Moen, J., Watermann, J., Alleyne, H., André, M., Dunlop, M. W., Cornilleau-Wehrlin, N., Masson, A., Fazerkerley, A., Rème, H., André, R., Amm, O., Balogh, A., Behlke, R., Blelly, P. L., Boholm, H., Borälv, E., Bosqued, J. M., Buchert, S., Candidi, M., Cerisier, J. C., Cully, C., Denig, W. F., Eglitis, P., Greenwald, R. A., Jackal, B., Kelly, J. D., Krauklis, I., Lu, G., Mann, I. R., Marcucci, M. F., McCrea, I. W., Maksimovic, M., Massetti, S., Décréau, P. M. E., Milling, D. K., Orsini, S., Pitout, F., Provan, G., Ruohoniemi, J. M., Samson, J. C., Schott, J. J., Sedgemore-Schulthess, F., Stamper, R., Stauning, P., Strömme, A., Taylor, M., Vaivads, A., Villain, J. P., Voronkov, I., Wild, J. A., Wild, M., Opgenoorth, H. J., Lockwood, M., Alcaydé, D., Donovan, E., Engebretson, M. J., van Eyken, A. P., Kauristie, K., Lester, M., Moen, J., Watermann, J., Alleyne, H., André, M., Dunlop, M. W., Cornilleau-Wehrlin, N., Masson, A., Fazerkerley, A., Rème, H., André, R., Amm, O., Balogh, A., Behlke, R., Blelly, P. L., Boholm, H., Borälv, E., Bosqued, J. M., Buchert, S., Candidi, M., Cerisier, J. C., Cully, C., Denig, W. F., Eglitis, P., Greenwald, R. A., Jackal, B., Kelly, J. D., Krauklis, I., Lu, G., Mann, I. R., Marcucci, M. F., McCrea, I. W., Maksimovic, M., Massetti, S., Décréau, P. M. E., Milling, D. K., Orsini, S., Pitout, F., Provan, G., Ruohoniemi, J. M., Samson, J. C., Schott, J. J., Sedgemore-Schulthess, F., Stamper, R., Stauning, P., Strömme, A., Taylor, M., Vaivads, A., Villain, J. P., Voronkov, I., Wild, J. A., and Wild, M.

Abstract

On 14 January 2001, the four Cluster spacecraft passed through the northern magnetospheric mantle in close conjunction to the EISCAT Svalbard Radar (ESR) and approached the post-noon dayside magnetopause over Greenland between 13:00 and 14:00 UT. During that interval, a sudden reorganisation of the high-latitude dayside convection pattern accurred after 13:20 UT, most likely caused by a direction change of the Solar wind magnetic field. The result was an eastward and poleward directed flow-channel, as monitored by the SuperDARN radar network and also by arrays of ground-based magnetometers in Canada, Greenland and Scandinavia. After an initial eastward and later poleward expansion of the flow-channel between 13:20 and 13:40 UT, the four Cluster spacecraft, and the field line footprints covered by the eastward looking scan cycle of the Sondre Stromfjord incoherent scatter radar were engulfed by cusp-like precipitation with transient magnetic and electric field signatures. In addition, the EISCAT Svalbard Radar detected strong transient effects of the convection reorganisation, a poleward moving precipitation, and a fast ion flow-channel in association with the auroral structures that suddenly formed to the west and north of the radar. From a detailed analysis of the coordinated Cluster and ground-based data, it was found that this extraordinary transient convection pattern, indeed, had moved the cusp precipitation from its former pre-noon position into the late post-noon sector, allowing for the first and quite unexpected encounter of the cusp by the Cluster spacecraft. Our findings illustrate the large amplitude of cusp dynamics even in response to moderate solar wind forcing. The global ground-based data proves to be an invaluable tool to monitor the dynamics and width of the affected magnetospheric regions.

Published
2001

22. Coordinated ground-based, low altitude satellite and Cluster observations on global and local scales during a transient post-noon sector excursion of the magnetospheric cusp

Author

Opgenoorth, H. J., primary, Lockwood, M., additional, Alcaydé, D., additional, Donovan, E., additional, Engebretson, M. J., additional, van Eyken, A. P., additional, Kauristie, K., additional, Lester, M., additional, Moen, J., additional, Waterman, J., additional, Alleyne, H., additional, André, M., additional, Dunlop, M. W., additional, Cornilleau-Wehrlin, N., additional, Masson, A., additional, Fazerkerley, A., additional, Rème, H., additional, André, R., additional, Amm, O., additional, Balogh, A., additional, Behlke, R., additional, Blelly, P. L., additional, Boholm, H., additional, Borälv, E., additional, Bosqued, J. M., additional, Buchert, S., additional, Candidi, M., additional, Cerisier, J. C., additional, Cully, C., additional, Denig, W. F., additional, Eglitis, P., additional, Greenwald, R. A., additional, Jackal, B., additional, Kelly, J. D., additional, Krauklis, I., additional, Lu, G., additional, Mann, I. R., additional, Marcucci, M. F., additional, McCrea, I. W., additional, Maksimovic, M., additional, Massetti, S., additional, Décréau, P. M. E., additional, Milling, D. K., additional, Orsini, S., additional, Pitout, F., additional, Provan, G., additional, Ruohoniemi, J. M., additional, Samson, J. C., additional, Schott, J. J., additional, Sedgemore-Schulthess, F., additional, Stamper, R., additional, Stauning, P., additional, Strømme, A., additional, Taylor, M., additional, Vaivads, A., additional, Villain, J. P., additional, Voronkov, I., additional, Wild, J. A., additional, and Wild, M., additional

Published
2001
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24. DFT modeling of Mn charged states in GaMnAs diluted ferromagnetic semiconductors: The cluster approach.

Author

Krauklis, I., Podkopaeva, O., and Chizhov, Yu.

Subjects
FERROMAGNETIC materials, SEMICONDUCTORS, AB-initio calculations, DENSITY functional theory, PARAMAGNETIC resonance, IMPURITY centers
Abstract

Quantum chemical cluster modeling of the high-symmetry nanoclusters GaMnAsH and GaMnAsH simulating the bulk of a GaAs crystal with Mn paramagnetic impurity center is carried out within the Density Functional Theory. A Generalized Gradient Approximation method PBEPBE/LanL2DZ is used to study the neutral Mn and ionized Mn states of a Mn atom in the nanoclusters under consideration. The change of the charge state of the impurity center from Mn to Mn leads to a considerable relaxation of Mn-As bonds in the immediate surroundings of the Mn atom and to the ' p-hole' recombination. It also affects the spin density localization. The components of the g-tensor for both the neutral Mn and the ionized Mnstates are calculated by the Gauge-Independent Atomic Orbital (GIAO) method with the hybrid density-functional mPW1PW91. The resulting values of the g-factor are in good agreement with the experimental Electron Paramagnetic Resonance data. The results obtained confirm the applicability of the cluster approach for describing charge effects in dilute ferromagnetic semiconductors. [ABSTRACT FROM AUTHOR]

Published
2014
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30. Linkage isomerism of CO adsorbed on alkali halides.

Author

Belykh R, Maevskaya M, Krauklis I, and Tsyganenko A

Abstract

Variable-temperature FTIR spectra of CO adsorbed on NaCl and KBr films are shown to reveal linkage isomerism, that is, formation of C- and O-bonded adsorption complexes with the same cationic sites. Not all of the sites can be involved in that, only the three- or four-coordinated cations located on kinks, edges, or steps of microcrystals. For NaCl, these adsorption complexes account for the high-frequency (HF) C-O stretching bands at 2175 and 2160 cm(-1). Coresponding LF bands of O-bonded CO were found at 2115 and 2124 cm(-1). In the spectrum of KBr, the HF band is poorly resolved, and only one LF band can be clearly seen, near 2124 cm(-1). The value of the isomerization enthalpy for complexes that account for the bands at 2160 and 2124 cm(-1) of CO adsorbed on NaCl, estimated from the experiment, is 4.0 ± 0.2 kJ/mol. Quantum mechanical calculations by DFT methods applied to NaCl model clusters interacting with the CO molecule confirm the existence of two potential wells with adsorption and isomerization energies close to the experimentally measured values, and enable us to estimate the height of the potential barrier between the two adsorption states.

Published
2015
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