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  • 1.
    Kim, Kyung Hwan
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Pathak, Harshad
    Stockholm University, Faculty of Science, Department of Physics.
    Späh, Alexander
    Stockholm University, Faculty of Science, Department of Physics.
    Perakis, Fivos
    Stockholm University, Faculty of Science, Department of Physics.
    Mariedahl, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Sellberg, Jonas A.
    Katayama, Tetsuo
    Harada, Yoshihisa
    Ogasawara, Hirohito
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    Temperature-Independent Nuclear Quantum Effects on the Structure of Water2017In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 119, no 7, article id 075502Article in journal (Refereed)
    Abstract [en]

    Nuclear quantum effects (NQEs) have a significant influence on the hydrogen bonds in water and aqueous solutions and have thus been the topic of extensive studies. However, the microscopic origin and the corresponding temperature dependence of NQEs have been elusive and still remain the subject of ongoing discussion. Previous x-ray scattering investigations indicate that NQEs on the structure of water exhibit significant temperature dependence [Phys. Rev. Lett. 94, 047801 (2005)]. Here, by performing wide-angle x-ray scattering of H2O and D2O droplets at temperatures from 275 K down to 240 K, we determine the temperature dependence of NQEs on the structure of water down to the deeply supercooled regime. The data reveal that the magnitude of NQEs on the structure of water is temperature independent, as the structure factor of D2O is similar to H2O if the temperature is shifted by a constant 5 K, valid from ambient conditions to the deeply supercooled regime. Analysis of the accelerated growth of tetrahedral structures in supercooled H2O and D2O also shows similar behavior with a clear 5 K shift. The results indicate a constant compensation between NQEs delocalizing the proton in the librational motion away from the bond and in the OH stretch vibrational modes along the bond. This is consistent with the fact that only the vibrational ground state is populated at ambient and supercooled conditions.

  • 2.
    Kim, Kyung Hwan
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Späh, Alexander
    Stockholm University, Faculty of Science, Department of Physics.
    Pathak, Harshad
    Stockholm University, Faculty of Science, Department of Physics.
    Perakis, Fivos
    Stockholm University, Faculty of Science, Department of Physics.
    Mariedahl, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Amann-Winkel, Katrin
    Stockholm University, Faculty of Science, Department of Physics.
    Sellberg, Jonas A.
    Lee, Jae Hyuk
    Kim, Sangsoo
    Park, Jaehyun
    Nam, Ki Hyun
    Katayama, Tetsuo
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    Maxima in the thermodynamic response and correlation functions of deeply supercooled water2017In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 358, no 6370, p. 1589-1593Article in journal (Refereed)
    Abstract [en]

    Femtosecond x-ray laser pulses were used to probe micrometer-sized water droplets that were cooled down to 227 kelvin in vacuum. Isothermal compressibility and correlation length were extracted from x-ray scattering at the low-momentum transfer region. The temperature dependence of these thermodynamic response and correlation functions shows maxima at 229 kelvin for water and 233 kelvin for heavy water. In addition, we observed that the liquids undergo the fastest growth of tetrahedral structures at similar temperatures. These observations point to the existence of a Widom line, defined as the locus of maximum correlation length emanating from a critical point at positive pressures in the deeply supercooled regime. The difference in the maximum value of the isothermal compressibility between the two isotopes shows the importance of nuclear quantum effects.

  • 3.
    Mariedahl, Daniel
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Perakis, Fivos
    Stockholm University, Faculty of Science, Department of Physics.
    Späh, Alexander
    Stockholm University, Faculty of Science, Department of Physics.
    Pathak, Harshad
    Stockholm University, Faculty of Science, Department of Physics.
    Kim, Kyung Hwan
    Stockholm University, Faculty of Science, Department of Physics.
    Benmore, Chris
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    Amann-Winkel, Katrin
    Stockholm University, Faculty of Science, Department of Physics.
    X-ray studies of the transformation from high- to low-density amorphous water2019In: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 377, no 2146, article id 20180164Article in journal (Refereed)
    Abstract [en]

    Here we report about the structural evolution during the conversion from high-density amorphous ices at ambient pressure to the low-density state. Using high-energy X-ray diffraction, we have monitored the transformation by following in reciprocal space the structure factor SOO(Q) and derived in real space the pair distribution function gOO(r). Heating equilibrated high-density amorphous ice (eHDA) at a fast rate (4Kmin-1), the transition to the low-density form occurs very rapidly, while domains of both high-and low-density coexist. On the other hand, the transition in the case of unannealed HDA (uHDA) and very-high-density amorphous ice is more complex and of continuous nature. The direct comparison of eHDA and uHDA indicates that the molecular structure of uHDA contains a larger amount of tetrahedral motives. The different crystallization behaviour of the derived low-density amorphous states is interpreted as emanating from increased tetrahedral coordination present in uHDA. This article is part of the theme issue 'The physics and chemistry of ice: scaffolding across scales, from the viability of life to the formation of planets'.

  • 4.
    Mariedahl, Daniel
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Perakis, Fivos
    Stockholm University, Faculty of Science, Department of Physics.
    Späh, Alexander
    Stockholm University, Faculty of Science, Department of Physics.
    Pathak, Harshad
    Stockholm University, Faculty of Science, Department of Physics.
    Kim, Kyung Hwan
    Stockholm University, Faculty of Science, Department of Physics.
    Camisasca, Gaia
    Stockholm University, Faculty of Science, Department of Physics.
    Schlesinger, Daniel
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Benmore, Chris
    Pettersson, Lars Gunnar Moody
    Stockholm University, Faculty of Science, Department of Physics.
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    Arnann-Winkel, Katrin
    Stockholm University, Faculty of Science, Department of Physics.
    X-ray Scattering and O-O Pair-Distribution Functions of Amorphous Ices2018In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 122, no 30, p. 7616-7624Article in journal (Refereed)
    Abstract [en]

    The structure factor and oxygen-oxygen pair distribution functions of amorphous ices at liquid nitrogen temperature (T = 77 K) have been derived from wide-angle X-ray scattering (WAXS) up to interatomic distances of r = 23 angstrom, where local structure differences between the amorphous ices can be seen for the entire range. The distances to the first coordination shell for low-, high-, and very-high-density amorphous ice (LDA, HDA, VHDA) were determined to be 2.75, 2.78, and 2.80 angstrom, respectively, with high accuracy due to measurements up to a large momentum transfer of 23 angstrom(-1). Similarities in pair-distribution functions between LDA and supercooled water at 254.1 K, HDA and liquid water at 365.9 K, and VHDA and high-pressure liquid water were found up to around 8 angstrom, but beyond that at longer distances, the similarities were lost. In addition, the structure of the high-density amorphous ices was compared to high-pressure crystalline ices IV, IX, and XII, and conclusions were drawn about the local ordering.

  • 5.
    Pathak, Harshad
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Späh, Alexander
    Stockholm University, Faculty of Science, Department of Physics.
    Kim, Kyung Hwan
    Stockholm University, Faculty of Science, Department of Physics.
    Tsironi, Ifigeneia
    Stockholm University, Faculty of Science, Department of Physics.
    Mariedahl, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Blanco, Maria
    Huotari, Simo
    Honkimäki, Veijo
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    Intermediate range O-O correlations in supercooled water down to 235 K2019In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 150, no 22, article id 224506Article in journal (Refereed)
    Abstract [en]

    Wide angle x-ray scattering of supercooled water down to 234.8 K was studied using high energy x rays at the European Synchrotron Radiation Facility. The oxygen-oxygen pair distribution function (PDF) was calculated from the scattering pattern out to the 5th peak at an intermolecular distance, r approximate to 11 angstrom. We observe that the 4th peak and the 5th peak in the PDF increase in height upon supercooling. We also observe that the 4th peak position (r(4)) shifts to shorter distances upon supercooling consistent with previous studies, but we see a more rapid change at the lowest temperature. The running oxygen-oxygen coordination number is calculated for 5 different temperatures, and an isosbestic point at r(iso) = 3.31 +/- 0.05 angstrom was found corresponding to a coordination number of 4.39 +/- 0.15. The comparison of the PDF of the coldest water with that of amorphous ice shows distinct differences. We propose that there are 5-member pentamer rings in low density liquid-like structures giving rise to the sharp correlations at r approximate to 9 angstrom and r approximate to 11 angstrom.

  • 6.
    Perakis, Fivos
    et al.
    Stockholm University, Faculty of Science, Department of Physics. SLAC National Accelerator Laboratory, USA.
    Amann-Winkel, Katrin
    Stockholm University, Faculty of Science, Department of Physics.
    Lehmkühler, Felix
    Sprung, Michael
    Mariedahl, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Sellberg, Jonas A.
    Pathak, Harshad
    Stockholm University, Faculty of Science, Department of Physics.
    Späh, Alexander
    Stockholm University, Faculty of Science, Department of Physics.
    Cavalca, Filippo
    Stockholm University, Faculty of Science, Department of Physics. SLAC National Accelerator Laboratory, USA.
    Schlesinger, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Ricci, Alessandro
    Jain, Avni
    Massani, Bernhard
    Aubree, Flora
    Benmore, Chris J.
    Loerting, Thomas
    Grübel, Gerhard
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    Diffusive dynamics during the high-to-low density transition in amorphous ice2017In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 114, no 31, p. 8193-8198Article in journal (Refereed)
    Abstract [en]

    Water exists in high- and low-density amorphous ice forms (HDA and LDA), which could correspond to the glassy states of high(HDL) and low-density liquid (LDL) in the metastable part of the phase diagram. However, the nature of both the glass transition and the high-to-low-density transition are debated and new experimental evidence is needed. Here we combine wide-angle X-ray scattering (WAXS) with X-ray photon-correlation spectroscopy (XPCS) in the small-angle X-ray scattering (SAXS) geometry to probe both the structural and dynamical properties during the high-to-low-density transition in amorphous ice at 1 bar. By analyzing the structure factor and the radial distribution function, the coexistence of two structurally distinct domains is observed at T = 125 K. XPCS probes the dynamics in momentum space, which in the SAXS geometry reflects structural relaxation on the nanometer length scale. The dynamics of HDA are characterized by a slow component with a large time constant, arising from viscoelastic relaxation and stress release from nanometer-sized heterogeneities. Above 110 K a faster, strongly temperature-dependent component appears, with momentum transfer dependence pointing toward nanoscale diffusion. This dynamical component slows down after transition into the low-density form at 130 K, but remains diffusive. The diffusive character of both the high- and low-density forms is discussed among different interpretations and the results are most consistent with the hypothesis of a liquid-liquid transition in the ultraviscous regime.

  • 7.
    Späh, Alexander
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Pathak, Harshad
    Stockholm University, Faculty of Science, Department of Physics.
    Kim, Kyung Hwan
    Stockholm University, Faculty of Science, Department of Physics.
    Perakis, Fivos
    Stockholm University, Faculty of Science, Department of Physics.
    Mariedahl, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Amann-Winkel, Katrin
    Stockholm University, Faculty of Science, Department of Physics.
    Sellberg, Jonas A.
    Lee, Jae Hyuk
    Kim, Sangsoo
    Park, Jaehyun
    Nam, Ki Hyun
    Katayama, Tetsuo
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    Apparent power-law behavior of water's isothermal compressibility and correlation length upon supercooling2019In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 21, no 1, p. 26-31Article in journal (Refereed)
    Abstract [en]

    The isothermal compressibility and correlation length of supercooled water obtained from small-angle X-ray scattering (SAXS) were analyzed by fits based on an apparent power-law in the temperature range from 280 K down to the temperature of maximum compressibility at 229 K. Although the increase in thermodynamic response functions is not towards a critical point, it is still possible to obtain an apparent power law all the way to the maximum values with best-fit exponents of gamma = 0.40 +/- 0.01 for the isothermal compressibility and nu = 0.26 +/- 0.03 for the correlation length. The ratio between these exponents is close to a value of approximate to 0.5, as expected for a critical point, indicating the proximity of a potential second critical point. Comparison of gamma obtained from experiment with molecular dynamics simulations on the iAMOEBA water model shows that it would be located at pressures in the neighborhood of 1 kbar. The high value and sharpness of the compressibility maximum observed in the experiment are not reproduced by any of the existing classical water models, thus inviting further development of simulation models of water.

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