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Bound by long-range...
Bound by long-range interactions: Molecular crystals and benzene on Cu(111)
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- Berland, Kristian, 1983 (författare)
- Chalmers tekniska högskola,Chalmers University of Technology
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(creator_code:org_t)
- 2009
- Engelska.
- Relaterad länk:
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https://research.cha...
Abstract
Ämnesord
Stäng
- This thesis investigates molecular systems bound by long-range interactions. Westudy molecular crystals held together by van der Waals forces and the physisorption of benzene (Bz) on Cu(111). We also study the self-organization of benzeneon the Cu(111) surface which is influenced both by the (semi) long-range van derWaals forces, and the very-long-ranged indirect electronic interactions mediated bya metallic surface state on the Cu(111) surface. The van der Waals bound systems are investigated from first-principle principlesusing a van der Waals density functional (vdW-DF), [Phys. Rev. Lett. 92, 246401 (2004)]. We examine the character of these interactions, by studying the asymptoticaccount of the van der Waals forces, and compare full vdW-DF with an asymptotic atom-based pair potentials extracted from vdW-DF. The results show that the charac-ter of the binding differs in the two cases, with vdW-DF being significantly enhanced at relevant binding separations. This suggests that the use of asymptotic atom-based pair potentials as an approximation for non-local correlation is not consistent. Formolecular crystals, we study the structure and cohesive energy of hexamine and the platonic hydrocarbons cubane and dodecahedrane. The calculated lattice parame-ters and cohesion energy agree well with experiments. For adsorption of benzene on Cu(111), we obtain a binding energy in good agreement with experiment. We alsostudy diffusion barriers and find that the molecules can move almost freely along a honeycomb web of “corridors” passing between fcc and hcp hollow sites via bridgesites. To account for the surface-state mediated interactions, we use a formal Harris-functional approach to evaluate nonperturbationally the asymptotic form of this in-direct interaction. This description is based on input from DFT calculations of the metallic surface state on Cu(111), in addition to a parameterization of the benzene-induced scattering properties. We combine vdW-DF calculations of benzene dimers and diffusion barriers with the estimates of the surface-state mediated interactionsand find that the more compact (hexagonal) Bz-overlayer phase, with lattice constant ̊a = 6.74 A, is due to direct Bz-Bz vdW attraction, and the stability of the sparser hexagonal Bz phase, a = 10.24 A, is due to surface-state mediated interactions. Thus, we can account well for benzene self-organization on Cu(111). These results illustrate the current state of development of quantum-physical based approaches to systems bound by long-range interactions.
Ämnesord
- NATURVETENSKAP -- Kemi -- Fysikalisk kemi (hsv//swe)
- NATURAL SCIENCES -- Chemical Sciences -- Physical Chemistry (hsv//eng)
- NATURVETENSKAP -- Fysik -- Annan fysik (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Other Physics Topics (hsv//eng)
- NATURVETENSKAP -- Fysik -- Den kondenserade materiens fysik (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Condensed Matter Physics (hsv//eng)
Nyckelord
- DFT
- diffusion barriers
- sparse matter
- platonic hydrocarbons
- molecular crystals
- van der Waals density functional (vdW-DF)
- van der Waals forces
- London-dispersion forces
- self-assembly
- hexamine
- molecular overlayers
- electronic structure
- Friedel oscillations
- soft matter
- surface-mediated interactions
- physiosorption
Publikations- och innehållstyp
- lic (ämneskategori)
- vet (ämneskategori)
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