J. Swenson

Chalmers University of Technology, Physics, Faculty Member

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Papers by J. Swenson

Predictability of ion transport properties from the structure of solid electrolytes

Ionics, 2004

The concept of bond valence (BV) is widely used in crystal chemical considerations, e.g. to asses... more The concept of bond valence (BV) is widely used in crystal chemical considerations, e.g. to assess equilibrium positions of atoms in crystal structures from an empirical relationship between bond length RM_x and bond valence SAX = exp [(Ro-RM_x) / b] as sites where the BV sum V(A) = ~ SM_x equals the formal valence Vid of the cation M § Our modified BV approach that systematically accounts for the softness of the bond may then be effectively used to study the interplay between structure and properties of solid electrolytes. This is exemplified for correlations to experimental data from IR, NMR, and impedance spectroscopy. Combining the bond valence approach with reverse Monte Carlo (RMC) modeling or molecular dynamics (MD) simulations provides a deeper understanding of ion transport mechanisms, especially in highly disordered or amorphous solids. Local structure models for crystalline electrolytes are derived by combining crystallographic structure information with simulations. A method for the prediction of the activation energy of the ionic conductivity from the bond valence analysis of the crystal structure is proposed. Taking into account the mass dependence of the conversion factor from bond valence mismatch into an activation energy scale, we could establish a correlation that holds for different types of mobile ions. The strong coupling of the H + transfer to the anion motion in proton conductors requires a special treatment. For glassy solid electrolytes RMC structure models are BV-analyzed to assess the total number of equilibrium sites and to identify transport pathways for the mobile ions. Recently, we have reported a correlation between the pathway volume fraction and the transport properties that permits to predict both absolute value and activation energy of the dc ionic conductivities of disordered solids (including mixed alkali glasses) directly from their structural models. Here we discuss a corresponding BV analysis of molecular dynamics simulation trajectories that allows quantifying the evolution of pathways in time and the influence of temperature on the transport pathways.

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The nature of conduction pathways in mixed alkali phosphate glasses

Ionics, 2004

In this paper we discuss the nature of the ion conduction pathways in LixRbl_xPO 3 glasses. Our i... more In this paper we discuss the nature of the ion conduction pathways in LixRbl_xPO 3 glasses. Our investigations are based on a bond valence analysis of reverse Monte Carlo (RMC) produced structural models in quantitative agreement with neutron and X-ray diffraction data. In a previous letter [11] we have shown that this approach enables us to reproduce and understand the mixed alkali effect (MAE) directly from the structural models. The results have shown that the drastic drop of the conductivity for an intermediate composition (x ~ 0.5) is mainly caused due to the blocking by immobile unlike cations, which is highly effective since the two types of alkali ions are randomly mixed and have distinctly different conduction pathways of low dimensionality. Here, we explore the local dimensionality of the pathways and discuss its implications for the network of pathways and the related ionic conductivity.

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Migration pathways in Ag-based superionic glasses and crystals investigated by the bond valence method

Physical Review B, 2000

The bond valence technique has been applied on reverse Monte Carlo produced structural models of ... more The bond valence technique has been applied on reverse Monte Carlo produced structural models of Agbased superionic glasses and crystals. The results for the ͑AgI͒ 0.75-͑Ag 2 MoO 4 ͒ 0.25 and ͑AgI͒ 0.6-͑Ag 2 O-2B 2 O 3 ͒ 0.4 glasses show the importance of including Ag sites with a high oxide coordination for the long-range mobility. The majority of the Ag ϩ ions belonging to the long-range conduction pathways is coordinated to both O and I Ϫ , and the pathways including only iodide coordinated sites are restricted to very local regions of a few Å. The most important finding of the present study is that the ionic conductivity as well as its activation energy can be determined directly from the ''pathway volume'' ͑i.e., the volume fraction of the percolating pathway cluster͒ of the structural models. The conductivity pathway volume relation is found to hold for glassy and crystalline conductors ͑including their temperature dependencies͒, whose conductivities differ by more than 11 orders of magnitude.

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The structure and dynamics of 2-dimensional fluids in swelling clays

Chemical Geology, 2006

The interlayer pores of swelling 2:1 clays provide an ideal 2-dimensional environment in which to... more The interlayer pores of swelling 2:1 clays provide an ideal 2-dimensional environment in which to study confined fluids. In this paper we discuss our understanding of the structure and dynamics of interlayer fluid species in expanded clays, based primarily on the outcome of recent molecular modelling and neutron scattering studies. Counterion solvation is compared with that measured in bulk solutions, and at a local level the cation-oxygen coordination is found to be remarkably similar in these two environments. However, for the monovalent ions the contribution to the first coordination shell from the clay surfaces increases with counterion radius. This gives rise to inner-sphere (surface)

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Evidence of Coupling between the Motions of Water and Peptides

The Journal of Physical Chemistry Letters, 2016

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DOPC versus DOPE as a helper lipid for gene-therapies: molecular dynamics simulations with DLin-MC3-DMA

Physical Chemistry Chemical Physics

A comparison of behavior of DOPC and DOPE lipids in the shell of lipid nano-particles.

format_quoteDLin-MC3-DMA showed the best gene-silencing activity in siRNA LNPs with DSPC, cholesterol, and pegylated lipids.format_quote

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Possible Relations between Supercooled and Glassy Confined Water and Amorphous Bulk Ice

Physical Chemistry Chemical Physics

In this paper we discuss apparent contradictions in the literature between dynamical results on s... more

format_quoteConfined water shows an absence of typical calorimetric glass transition, complicating analysis across various data methods.format_quote

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The application of reverse Monte Carlo modelling to a polymeric melt

Computational and Theoretical Polymer Science

ABSTRACT

$Research paper thumbnail of Structure of multi component glasses using diffraction techniques and reverse Monte Carlo modelling$

Structure of multi component glasses using diffraction techniques and reverse Monte Carlo modelling

Structural properties of glasses in general, and complicated multi component glasses in particula... more Structural properties of glasses in general, and complicated multi component glasses in particular, are difficult to extract directly from experimental results. This is partly because global structural investigations by diffraction techniques are only providing a one-dimensional average representation of the structure, usually without any information of partial pair correlations for a single experiment. Furthermore, many glasses are so chemically complicated that it has, so far, been difficult to develop interatomic model potentials between the particles that are accurate enough for reproducing the diffraction data using conventional simulation techniques such as molecular dynamics (MD) and Monte Carlo (MC) simulations. The reverse Monte Carlo (RMC) modelling method overcomes the problem of finding model potentials and instead it makes direct use of the available experimental data. In this way, the RMC method produces three dimensional structural models which are quantitatively consistent with the available data and the applied constraint, e.g. constraints of density, minimum atomic sizes and coordination numbers. As an illustrative example, we show how the RMC method has been used for structural modelling of the fast ion conducting glasses (AgI)0.6(Ag2O-2B2O3)0.4 and (AgI)0.75(Ag2MoO4)0.25. Some advantages and limitations of the method will also be discussed.

Water structure and dynamics in a fully hydrated sodium vermiculite clay

Philosophical Magazine B, 2002

We have investigated the structure and dynamics of confined water in a fully hydrated sodium verm... more We have investigated the structure and dynamics of confined water in a fully hydrated sodium vermiculite clay by neutron diffraction and neutron spin-echo (NSE) spectroscopy. All measurements were performed with the Q vector parallel to the clay layers. In the case of the diffraction experiments we used both protonated and deuterated water in order to elucidate the interlayer water structure.

Relation between structural and conductivity relaxation in PEO and PEO based electrolytes

Solid State Ionics, 2014

Structure of Ca0.4K0.6(NO3)1.4 from the glass to the liquid state

Physical Review B, 2001

Structure of Borate Glasses

$Research paper thumbnail of Inhomogeneous, disordered, and partially ordered systems-Structure of mixed alkali/alkaline-earth silicate glasses from neutron diffraction and vibrational spectroscopy$

Inhomogeneous, disordered, and partially ordered systems-Structure of mixed alkali/alkaline-earth silicate glasses from neutron diffraction and vibrational spectroscopy

Dynamics of hemoglobin in different solvents as studied by QENS and Dielectric Spectroscopy

Application of the bond valence method to reverse Monte Carlo produced structural models of superionic glasses