| 1. |
- Bostrom, Mathias, et al.
(författare)
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Lifshitz interaction can promote ice growth at water-silica interfaces
- 2017
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 95:15
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Tidskriftsartikel (refereegranskat)abstract
- At air-water interfaces, the Lifshitz interaction by itself does not promote ice growth. On the contrary, we find that the Lifshitz force promotes the growth of an ice film, up to 1-8 nm thickness, near silica-water interfaces at the triple point of water. This is achieved in a system where the combined effect of the retardation and the zero frequency mode influences the short-range interactions at low temperatures, contrary to common understanding. Cancellation between the positive and negative contributions in the Lifshitz spectral function is reversed in silica with high porosity. Our results provide a model for how water freezes on glass and other surfaces.
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| 2. |
- Bostrom, Mathias, et al.
(författare)
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Self-preserving ice layers on CO2 clathrate particles : Implications for Enceladus, Pluto, and similar ocean worlds
- 2021
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 650
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Tidskriftsartikel (refereegranskat)abstract
- Context. Gas hydrates can be stabilised outside their window of thermodynamic stability by the formation of an ice layer - a phenomenon termed self-preservation. This can lead to a positive buoyancy for clathrate particles containing CO2 that would otherwise sink in the oceans of Enceladus, Pluto, and similar oceanic worlds.Aims. Here we investigate the implications of Lifshitz forces and low occupancy surface regions on type I clathrate structures for their self-preservation through ice layer formation, presenting a plausible model based on multi-layer interactions through dispersion forces.Methods. We used optical data and theoretical models for the dielectric response for water, ice, and gas hydrates with a different occupancy. Taking this together with the thermodynamic Lifshitz free energy, we modelled the energy minima essential for the formation of ice layers at the interface between gas hydrate and liquid water.Results. We predict the growth of an ice layer between 0.01 and 0.2 mu m thick on CO, CH4, and CO2 hydrate surfaces, depending on the presence of surface regions depleted in gas molecules. Effective hydrate particle density is estimated, delimiting a range of particle size and compositions that would be buoyant in different oceans. Over geological time, the deposition of floating hydrate particles could result in the accumulation of kilometre-thick gas hydrate layers above liquid water reservoirs and below the water ice crusts of their respective ocean worlds. On Enceladus, the destabilisation of near-surface hydrate deposits could lead to increased gas pressures that both drive plumes and entrain stabilised hydrate particles. Furthermore, on ocean worlds, such as Enceladus and particularly Pluto, the accumulation of thick CO2 or mixed gas hydrate deposits could insulate its ocean against freezing. In preventing freezing of liquid water reservoirs in ocean worlds, the presence of CO2-containing hydrate layers could enhance the habitability of ocean worlds in our Solar System and on the exoplanets and exomoons beyond.
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| 3. |
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| 4. |
- Boström, Mathias, et al.
(författare)
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Enlarged molecules from excited atoms in nanochannels
- 2012
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 86:1, s. 014701-
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Tidskriftsartikel (refereegranskat)abstract
- The resonance interaction that takes place in planar nanochannels between pairs of excited-state atoms is explored. We consider interactions in channels of silica, zinc oxide, and gold. The nanosized channels induce a dramatically different interaction from that in free space. Illustrative calculations for two lithium and cesium atoms demonstrate that there is a short-range repulsion followed by long-range attraction. The binding energy is strongest near the surfaces. The size of the enlarged molecule is biggest at the center of the cavity and increases with channel width. Since the interaction is generic, we predict that enlarged molecules are formed in porous structures, and that the molecule size depends on the size of the nanochannels.
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| 5. |
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| 6. |
- Boström, Mathias, et al.
(författare)
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Retardation turns the van der Waals attraction into a Casimir repulsion as close as 3 nm
- 2012
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 85:1, s. 010701-
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Tidskriftsartikel (refereegranskat)abstract
- Casimir forces between surfaces immersed in bromobenzene have recently been measured by Munday et al. [Nature (London) 454, 07610 (2009)]. Attractive Casimir forces were found between gold surfaces. The forces were repulsive between gold and silica surfaces. We show the repulsion is due to retardation effects. The van der Waals interaction is attractive at all separations. The retardation-driven repulsion sets in at around 3 nm. To our knowledge, retardation effects have never been found at such a small distance before. Retardation effects are usually associated with large distances.
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| 7. |
- Boström, Mathias, et al.
(författare)
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Sign of the Casimir-Polder interaction between atoms and oil-water interfaces: Subtle dependence on dielectric properties
- 2012
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 85:6, s. 064501-
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate that Casimir-Polder energies between noble gas atoms (dissolved in water) and oil-water interfaces are highly surface specific. Both repulsion (e.g., hexane) and attraction (e.g., glycerine and cyclodecane) is found with different oils. For several intermediate oils (e.g., hexadecane, decane, and cyclohexane) both attraction and repulsion can be found in the same system. Near these oil-water interfaces the interaction is repulsive in the nonretarded limit and turns attractive at larger distances as retardation becomes important. These highly surface specific interactions may have a role to play in biological systems where the surface may be more or less accessible to dissolved atoms.
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| 8. |
- Boström, Mathias, et al.
(författare)
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Ultrathin metallic coatings can induce quantum levitation between nanosurfaces
- 2012
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 100:25, s. 253104-
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Tidskriftsartikel (refereegranskat)abstract
- There is an attractive Casimir-Lifshitz force between two silica surfaces in a liquid (bromobenze or toluene). We demonstrate that adding an ultrathin (5-50 angstrom) metallic nanocoating to one of the surfaces results in repulsive Casimir-Lifshitz forces above a critical separation. The onset of such quantum levitation comes at decreasing separations as the film thickness decreases. Remarkably, the effect of retardation can turn attraction into repulsion. From that we explain how an ultrathin metallic coating may prevent nanoelectromechanical systems from crashing together.
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| 9. |
- Dou, Maofeng, et al.
(författare)
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Casimir quantum levitation tuned by means of material properties and geometries
- 2014
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 89:20, s. 201407-
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Tidskriftsartikel (refereegranskat)abstract
- The Casimir force between two surfaces is attractive in most cases. Although stable suspension of nano-objects has been achieved, the sophisticated geometries make them difficult to be merged with well-established thin film processes. We find that by introducing thin film surface coating on porous substrates, a repulsive to attractive force transition is achieved when the separations are increased in planar geometries, resulting in a stable suspension of two surfaces near the force transition separation. Both the magnitude of the force and the transition distance can be flexibly tailored though modifying the properties of the considered materials, that is, thin film thickness, doping concentration, and porosity. This stable suspension can be used to design new nanodevices with ultralow friction. Moreover, it might be convenient to merge this thin film coating approach with micro- and nanofabrication processes in the future.
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| 10. |
- Fiedler, Johannes, et al.
(författare)
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Effective Polarizability Models
- 2017
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 121:51, s. 9742-9751
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Tidskriftsartikel (refereegranskat)abstract
- Theories for the effective polarizability of a small particle in a medium are presented using different levels of approximation: we consider the virtual cavity, real cavity, and the hard-sphere models as well as a continuous interpolation of the latter two. We present the respective hard-sphere and-cavity radii as obtained from density-functional simulations as well as the resulting effective polarizabilities at discrete Matsubara frequencies. This enables us to account for macroscopic media in van der Waals interactions between molecules in water and their Casimir-Polder interaction with an interface.
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