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A study of finite-size, non-perturbative and anisotropic effects on the Lifshitz-van der Waals forces and torque with material dielectric responses from first-principles calculations
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.ORCID iD: 0000-0002-5249-0211
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The van der Waals and the Casimir-Lifshitz forces are forces of attraction that exist between neutral polarizable bodies due to quantum fluctuations. They can be repulsive depending on the material properties and the geometry of the system. Since they are pervasive in nature, they encompass a great deal of relevance in the study of interaction between bodies in several different scenarios and background geometrical settings.

 

This doctoral thesis first addresses the important aspects of finite-size and the non-perturbative effects of the van der Waals interactions between two atoms or molecules. Going beyond the usual assumption of atoms and molecules as point particles and adopting a description of finite size, the divergence inherent in such interaction energies in the limit of zero separation distance between the two interacting atoms or molecules is removed. The attainment of finite interaction energy at such close separation distance facilitates the estimation of van der Waals force contribution to the binding energy of the molecules, and towards surfaces. This is particularly important for noble atoms. The interaction between a pair of helium (He) atoms and krypton (Kr) atoms, and between a pair of methane (CH$_4$) molecules considering its environmental relevance, is investigated in detail. The application of finite size further leads to finite self energies of the atoms. The full expression of the interaction energy, as is discussed in detail in this thesis, typically contains a logarithmic factor of the form $\ln(1 \pm x)$. Formerly, in evaluating the interaction energies, this factor is customarily series-expanded and truncated in the leading order with certain assumptions. This thesis explores the effect of using the full expression, which is referred herein as the non-perturbative (or, the non-expanded) theory, analytically wherever possible as well as numerically. The combined application of the finite-size theory and the non-perturbative theory results in as much as 100\,\% correction in the self energy of atoms in vacuum. This may give rise to significant physical consequences, for example, in the permeabilities of atoms across dielectric membranes.

 

The thesis next addresses the aspect of anisotropy in the Casimir-Polder interaction between a completely polarizable molecule and a dielectric slab polarizable in the normal direction. The formalism is applied to the study of preferential adsorption in the specific case of carbon dioxide (CO$_2$) and methane (CH$_4$) molecules interacting with amorphous silica slabs and thin gold films. Owing to its greater polarizability, the linearly polarizable CO$_2$ molecule is found to attract more towards the surfaces than the isotropically polarizable CH$_4$ molecule. In addition, the stable orientation of the CO$_2$ molecule with respect to the surface is determined to be the one in which the long, linear axis of the molecule is perpendicular to the surface. Further, the feature of Casimir torque which is a consequence of anisotropy in the interacting dielectric slabs is explored in the case of biaxial materials, in particular the bulk black phosphorus and its novel 2D counterpart phosphorene. The torque between a pair of phosphorus slabs, one face rotated with respect to the other, is observed to change sign at a particular separation distance which is determined by the crossing frequency of its planar dielectric components. This distance-dependent reversal of the sign of torque has never been observed before. The observation is verified with several other biaxial materials. This finding will help assist in the experimental detection of the Casimir torque, and can potentially be exploited in the future for designing nanodevices.

 

Another remarkable effect that is uncovered is the submersion of ice microcrystals under water governed by the balance of repulsive Lifshitz force from the vapor-water interface and the buoyant force of water. The repulsive effect is found to be enhanced by the presence of salt ions in the system. An exclusion zone ranging from 2 nm to 1 ${\mu}$m devoid of small ice particles is formed below the water surface. As the ice sphere grows in size, the buoyant force overcomes the Lifshitz force, and the ice sphere starts to float with a fraction of its volume above the water surface in accordance with the classical Archimedes principle. The combined impact of Lifshitz forces and double-layer interactions is further investigated in ice-water-CO$_2$ and vapor-water-CO$_2$ systems  employing different models of effective polarizability for ions, {\it viz.} the hardsphere model and Onsager's model. The CO$_2$ bubble is found to be repelled by the vapor-water interface and attracted towards the ice-water interface. The equilibrium thin film of water formed between vapor and ice surfaces varies in thickness depending on the model of effective polarizability and the type of salt present in the system. Further studies of the interaction energy in geometries comprising two molecules near an interface and molecule in a three-layer geometry are conducted which may be relevant for potential energy storage applications. The density functional theory (DFT) is employed to generate the frequency-dependent dielectric functions required for Lifshitz energy and force calculations.

 

Summing up, in the numerous contexts outlined above, the importance of the van der Waals and Lifshitz forces has been demonstrated. The studies in this thesis enable significant predictions related to these forces which may be verifiable by experiments.

 

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2018. , p. 112
Series
TRITA-ITM-AVL ; 2018:16
Keywords [en]
Lifshitz-van der Waals forces, Casimir torque, optical calculations with density functional theory, phosphorus, phosphorene
National Category
Other Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-227041ISBN: 978-91-7729-789-5 (print)OAI: oai:DiVA.org:kth-227041DiVA, id: diva2:1202959
Public defence
2018-05-25, D3, Lindstedtsvägen 5, Stockholm, 13:15 (English)
Supervisors
Available from: 2018-05-02 Created: 2018-05-02 Last updated: 2019-01-07Bibliographically approved
List of papers
1. Finite-size-dependent dispersion potentials between atoms and ions dissolved in water
Open this publication in new window or tab >>Finite-size-dependent dispersion potentials between atoms and ions dissolved in water
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2014 (English)In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 106, no 5, p. 53002-Article in journal (Refereed) Published
Abstract [en]

A non-expanded theory is used for dispersion potentials between atoms and ions dissolved in a medium. The first-order dispersion interaction between two atoms in an excited state must account for the fact that the two atoms are coupled via the electromagnetic field and must include effects from background media, retardation and finite size. We show that finite-size corrections when two particles are close change the dispersion interactions in water by several orders of magnitude. We consider as four illustrative examples helium atoms, krypton atoms, phosphate ions, and iodide ions. We demonstrate that, due to large cancellation effects, retardation dominates the interaction for helium atom pairs in an isotropic excited state down to the very small atom-atom separations where finite-size corrections are also important.

Keywords
Correlated Molecular Calculations, Gaussian-Basis Sets, Energy
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-149225 (URN)10.1209/0295-5075/106/53002 (DOI)000339151800008 ()2-s2.0-84902171506 (Scopus ID)
Funder
Swedish Research Council, C0485101
Note

QC 20140818

Available from: 2014-08-18 Created: 2014-08-18 Last updated: 2018-05-02Bibliographically approved
2. Intermolecular Casimir-Polder forces in water and near surfaces
Open this publication in new window or tab >>Intermolecular Casimir-Polder forces in water and near surfaces
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2014 (English)In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 90, no 3, p. 032122-Article in journal (Refereed) Published
Abstract [en]

The Casimir-Polder force is an important long-range interaction involved in adsorption and desorption of molecules in fluids. We explore Casimir-Polder interactions between methane molecules in water, and between a molecule in water near SiO2 and hexane surfaces. Inclusion of the finite molecular size in the expression for the Casimir-Polder energy leads to estimates of the dispersion contribution to the binding energies between molecules and between one molecule and a planar surface.

Keywords
Casimir-Polder force, Near surfaces
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-154762 (URN)10.1103/PhysRevE.90.032122 (DOI)000342562600002 ()2-s2.0-84907279845 (Scopus ID)
Funder
Swedish Research Council, 90499401
Note

QC 20141104

Available from: 2014-11-04 Created: 2014-10-27 Last updated: 2018-05-02Bibliographically approved
3. Non-perturbative theory of dispersion interactions
Open this publication in new window or tab >>Non-perturbative theory of dispersion interactions
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2015 (English)In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 90, no 3, article id 035405Article in journal (Refereed) Published
Abstract [en]

Some open questions exist with fluctuation-induced forces between extended dipoles. Conventional intuition derives from large-separation perturbative approximations to dispersion force theory. Here, we present a full non-perturbative theory. In addition, we discuss how one can take into account finite dipole size corrections. It is of fundamental value to investigate the limits of validity of the perturbative dispersion force theory.

Keywords
fluctuation forces, non-perturbative theory, van der Waals interactions
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-163995 (URN)10.1088/0031-8949/90/3/035405 (DOI)000350866700023 ()2-s2.0-84924301472 (Scopus ID)
Funder
Swedish Research Council, C0485101
Note

QC 20150507

Available from: 2015-05-07 Created: 2015-04-13 Last updated: 2018-05-02Bibliographically approved
4. Nonperturbative theory for the dispersion self-energy of atoms
Open this publication in new window or tab >>Nonperturbative theory for the dispersion self-energy of atoms
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2014 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 90, no 5, p. 054502-Article in journal (Refereed) Published
Abstract [en]

We go beyond the approximate series expansions used in the dispersion theory of finite-size atoms. We demonstrate that a correct, and nonperturbative, theory dramatically alters the dispersion self-energies of atoms. The nonperturbed theory gives as much as 100% corrections compared to the traditional series-expanded theory for the smaller noble gas atoms.

National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-158403 (URN)10.1103/PhysRevA.90.054502 (DOI)000345414100014 ()2-s2.0-84910601102 (Scopus ID)
Note

QC 20150109

Available from: 2015-01-09 Created: 2015-01-07 Last updated: 2018-05-02Bibliographically approved
5. Trends of CO2 adsorption on cellulose due to van der Waals forces
Open this publication in new window or tab >>Trends of CO2 adsorption on cellulose due to van der Waals forces
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2015 (English)In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 470, p. 316-321Article in journal (Refereed) Published
Abstract [en]

The non-retarded van der Waals and Casimir-Polder forces on a CO2 molecule in water near a single surface and between surfaces are explored. We observe preferential adsorption and desorption of CO2 molecules depending on the material of the surfaces. We also find a potential mechanism of capture and storage of CO2 molecules in a geometry consisting of a cellulose surface coated by a thin film of water and then by air.

Keywords
Carbon capture and storage, Preferential adsorption, Casimir-Polder energy, Three-layered systems
National Category
Chemical Sciences Physical Sciences
Identifiers
urn:nbn:se:kth:diva-165196 (URN)10.1016/j.colsurfa.2014.12.044 (DOI)000351913800039 ()2-s2.0-84920842036 (Scopus ID)
Note

QC 20150507

Available from: 2015-05-07 Created: 2015-04-24 Last updated: 2018-05-02Bibliographically approved
6. Effects of van der Waals forces and salt ions on the growth of water films on ice and the detachment of CO2 bubbles
Open this publication in new window or tab >>Effects of van der Waals forces and salt ions on the growth of water films on ice and the detachment of CO2 bubbles
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2016 (English)In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 113, no 4, article id 43002Article in journal (Refereed) Published
Abstract [en]

We study the effect of salts on the thickness of wetting films on melting ice and interactions acting on CO2 bubble near ice-water and vapor-water interfaces. Governing mechanisms are the Lifshitz and the double-layer interactions in the respective three-layer geometries. We demonstrate that the latter depend on the Casimir-Polder interaction of the salt ions dissolved in water with the respective ice, vapor and CO2 interfaces, as calculated using different models for their effective polarizability in water. Significant variation in the predicted thickness of the equilibrium water film is observed for different salt ions and when using different models for the ions' polarizabilities. We find that CO2 bubbles are attracted towards the ice-water interface and repelled from the vapor-water interface.

Keywords
Lifshitz Theory, Hydrocarbon Adsorption, Vanderwaals Forces, Dispersion Forces, Liquid Helium, Surface, Dependence, Systems, Storage
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-185385 (URN)10.1209/0295-5075/113/43002 (DOI)000372420000012 ()2-s2.0-84962231437 (Scopus ID)
Note

QC 20160418

Available from: 2016-04-18 Created: 2016-04-18 Last updated: 2018-05-02Bibliographically approved
7. Effective lennard-jones parameters for CO2-CO2 dispersion interactions in water and near amorphous silica-water interfaces
Open this publication in new window or tab >>Effective lennard-jones parameters for CO2-CO2 dispersion interactions in water and near amorphous silica-water interfaces
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2015 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Different models for effective polarizability in water and the corresponding dispersion forces between dissolved molecules are explored in bulk water and near interfaces. We demonstrate that the attractive part of the Lennard-Jones parameters, i.e., the van der Waals parameter C6 (UvdW ≈ -C6/ρ6), is strongly modified when two carbon dioxide (CO2) molecules are near an amorphous silica-water and near a vapor-water interface. Standard simulation parameters for near-surface modeling are based on intermolecular forces in bulk media.

Place, publisher, year, edition, pages
Electromagnetics Academy, 2015
Keywords
Amorphous carbon, Carbon, Chemical bonds, Dispersions, Molecules, Silica, Van der Waals forces, Amorphous silica, Dispersion force, Dispersion interaction, Inter-molecular forces, Lennard-Jones parameters, Polarizabilities, Simulation parameters, Van der waals, Carbon dioxide
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-181587 (URN)2-s2.0-84947259599 (Scopus ID)9781934142301 (ISBN)
Conference
Progress in Electromagnetics Research Symposium
Note

QC 20160311

Available from: 2016-03-11 Created: 2016-02-02 Last updated: 2018-05-02Bibliographically approved
8. Anisotropic contribution to the van der Waals and the Casimir-Polder energies for CO2 and CH4 molecules near surfaces and thin films
Open this publication in new window or tab >>Anisotropic contribution to the van der Waals and the Casimir-Polder energies for CO2 and CH4 molecules near surfaces and thin films
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2015 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 92, no 5, article id 052704Article in journal (Refereed) Published
Abstract [en]

In order to understand why carbon dioxide (CO2) and methane (CH4) molecules interact differently with surfaces, we investigate the Casimir-Polder energy of a linearly polarizable CO2 molecule and an isotropically polarizable CH4 molecule in front of an atomically thin gold film and an amorphous silica slab. We quantitatively analyze how the anisotropy in the polarizability of the molecule influences the van der Waals contribution to the binding energy of the molecule.

Place, publisher, year, edition, pages
American Physical Society, 2015
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-177939 (URN)10.1103/PhysRevA.92.052704 (DOI)000364156300004 ()2-s2.0-84946944015 (Scopus ID)
Note

QC 20151203

Available from: 2015-12-03 Created: 2015-11-30 Last updated: 2018-05-02Bibliographically approved
9. Distance-Dependent Sign Reversal in the Casimir-Lifshitz Torque
Open this publication in new window or tab >>Distance-Dependent Sign Reversal in the Casimir-Lifshitz Torque
2018 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 120, no 131601Article in journal, Letter (Refereed) Published
National Category
Natural Sciences
Identifiers
urn:nbn:se:kth:diva-226959 (URN)10.1103/PhysRevLett.120.131601 (DOI)000428243400001 ()2-s2.0-85044837771 (Scopus ID)
Note

QC 20180515

Available from: 2018-04-30 Created: 2018-04-30 Last updated: 2018-05-31Bibliographically approved
10. Ice particles sink below the water surface due to a balance of salt, van der Waals and buoyancy forces
Open this publication in new window or tab >>Ice particles sink below the water surface due to a balance of salt, van der Waals and buoyancy forces
(English)Manuscript (preprint) (Other academic)
National Category
Natural Sciences
Identifiers
urn:nbn:se:kth:diva-226960 (URN)
Note

QC 20180523

Available from: 2018-04-30 Created: 2018-04-30 Last updated: 2018-05-23Bibliographically approved

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