Sökning: "vdW"

Visar resultat 1 - 5 av 16 avhandlingar innehållade ordet vdW.

1. 1. Density Functional Theory Calculations for Graphene-based Gas Sensor Technology

   Författare :Karim Elgammal; Anna Delin; Giuseppe Iannaccone; KTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; graphene; ab-initio; humidity; carbon dioxide; substrate; DFT; vdW; first-principle; simulation; calculations; Fysik; Physics;

   Sammanfattning : Nowadays, electronic devices span a diverse pool of applications, especially when getting smaller and smaller satisfying the more than Moore paradigm. To further develop this, studies focusing on material design toward electronic devices are crucial. LÄS MER

3. 2. Nonlocal Correlations in Density Functional Theory

   Författare :Henrik Rydberg; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; bonding; GGA; adhesion; graphene; DFT; exchange; adsorption; LDA; first principles; polarization; vdW; determinants; correlation; graphite; surface states; van der Waals; density-functional theory; physisorption; nonlocal; functional;

   Sammanfattning : In Density Functional Theory, the widely used local and semilocal approximations to the exchange-correlation energy, the local density approximation (LDA) and the generalized gradient approximations (GGAs), lack a physical description of truly nonlocal correlation effects, which are absolutely essential for a proper description of soft matter. A scheme is proposed that provides a basis for systematic improvements beyond LDA and GGA, including correlations at intermediate and long range, giving rise to bonds of pure van der Waals type as well as more intricate, intermediate-range correlation bonds. LÄS MER

4. 3. Bound by long-range interactions: Molecular crystals and benzene on Cu(111)

   Författare :Kristian Berland; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; 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;

   Sammanfattning : 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). LÄS MER

5. 4. Theory of van der Waals bonding: from bulk materials to biomolecules

   Författare :Elisa Londero; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; alkanes; extended systems; DNA; band structure; van der Waals Density Functional vdW-DF ; exchange functionals; Density Functional Theory; non-local correlation; layered oxides;

   Sammanfattning : Sparse matter is abundant in Nature.It encompasses systems characterized by an intrinsic low density of electrons in sizeable regions, where the van der Waals forces contribute considerably to cohesion.Given the length scale of the problem, a prediction of these materials requires appropriate tools within a quantum-mechanical framework. LÄS MER

7. 5. Formation stability and electronic structure of surfaces and interfaces from first principles

   Författare :Jochen Rohrer; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; NATURVETENSKAP; NATURAL SCIENCES; band structure; van der Waals interaction; electronic structure; graphane; graphene; atomic structure; growth; thin film; interface; density functional theory; CVD; Alumina; nucleation;

   Sammanfattning : This thesis deals with two closely interwoven aspects of first-principle(density functional theory) materials modeling:(1)~prediction of atomic structure & chemical composition,and (2)~prediction of electronic properties.In the first part, we focus on atomic structure (AS) and chemical composition (CC) of surface and interface systems. LÄS MER