Sökning: "DENSITY-FUNCTIONAL THEORY"

Visar resultat 21 - 25 av 586 avhandlingar innehållade orden DENSITY-FUNCTIONAL THEORY.

1. 21. Vibrational and Structural Characterisation in Two Perovskite Challenges: A Density Functional Theory Study

   Författare :Erik Jedvik Granhed; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; phonon; chemical expansion; materials modelling; oxyhydride; polaron; vibrational analysis; BaTiO3; BaZrO3; anti-ferrodistortive; density functional theory;

   Sammanfattning : The modelling of perovskites using density functional theory (DFT) can sometimes be a challenge with many different states very close in energy. In particular, the tilting of the inscribed octahedron, as well as the formation of electron polarons, leads to states with energy differences in the meV range. LÄS MER

3. 22. Micro-reaction Mechanism Study of the Biomass Thermal Conversion Process using Density Functional Theory

   Författare :Xiaolei Zhang; Weihong Yang; Linda J. Broadbelt; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; biomass thermal conversion; cellulose pyrolysis; char steam gasification; adsorption; interaction; mechanism; quantum chemistry; density functional theory;

   Sammanfattning : Biomass, or bio-energy, is one of the most important alternative energies because of environmental concerns and the future shortage of fossil fuels. Multi-scaled bioenergy studies have been performed in the division of Energy and Furnace Technology, which included studies of macroscopic systems such as systems and reactors, modeling of computational fluid dynamics (CFD), and atomic/molecular level studies. LÄS MER

4. 23. Van der Waals density-functional description of polymers and other sparse materials

   Författare :Jesper Kleis; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; softmatter; Density functional theory; polyethylene; van der Waals interaction; polymer crystal; nanotubes; DFT; sparse material systems; polymer interactions; polymer structure;

   Sammanfattning : Polymers are abundant in nature --- rubber, tar and latex have been known to mankind for thousands of years. Early in the 20th century, a systematic synthesis of polymers was developed, but the great potential of synthesized polymers was recognized first during World War II. LÄS MER

5. 24. Thermodynamic and kinetic properties of Fe-Cr and TiC-ZrC alloys from Density Functional Theory

   Författare :Vsevolod Razumovskiy; Pavel Korzhavyi; Andrei Ruban; Malin Selleby; Sergei Dudarev; KTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; ab initio; first principles; point defects; vacancy clusters; alloys; steels; iron; carbides; diffusion; phase diagram; density functional theory; elastic constants; elastic properties; thermodynamic modelling;

   Sammanfattning : The complete and accurate thermodynamic and kinetic description of any systemis crucialfor understanding and predicting its properties. A particular interest is in systemsthat are used for some practical applications and have to be constantly improved usingmodification of their composition and structure. LÄS MER

7. 25. Quantum aspects of hydrogen in metals and oxides from density-functional calculations

   Författare :Per G. Sundell; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; diffusion; density functional theory; hydrogen; quantum tunneling; electronic structure; perovskite oxide; metal; first-principles; DFT.; ab-initio;

   Sammanfattning : Atomic hydrogen dissolved in a solid or adsorbed on a solid surfacedisplays many remarkable features, and is a subject ofgreat technological interest.An increased understanding of hydrogen/solid systems can supportthe development of areas as diverse asproton exchange membranes for fuel cells,heterogeneous catalysis, and growth of semiconductor devices. LÄS MER