Sökning: "vibrational frequencies"

Visar resultat 1 - 5 av 45 avhandlingar innehållade orden vibrational frequencies.

1. 1. Surface Vibrational and Electron Spectroscopy - Experiments and first-principle calculations

   Författare :Martin Andersson; Kemisk fysik; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; gränsskikt; anharmonicity; Ytkemi; Surface and boundary layery chemistry; adsorbates; metal surface; density functional theory; first-principle calculations; electron spectroscopy; reflection-absorption infrared spectroscopy; vibrational spectroscpy;

   Sammanfattning : This work deals with interpretation of experimental surface spectroscopic data with the aid of first-principle calculations. Surface infrared reflection-absorption spectra as well as spectra from the electron spectroscopic methods photoemission and X-ray absorption are considered. LÄS MER

3. 2. Physisorption of CO and N2O on ceria surfaces

   Författare :Carsten Müller; Kersti Hermansson; Konstantin Neyman; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; ceria; carbon monoxide; nitrous oxide; embedded cluster; physisorption; method of increments; CCSD T ; vibrational frequencies; Quantum chemistry; Kvantkemi; Quantum Chemistry; kvantkemi;

   Sammanfattning : Physisorption of CO and N2O on surfaces of ceria (CeO2) was investigated by means of high-level quantum-mechanical embedded cluster calculations. Both systems have high relevance in the field of environmental chemistry and heterogeneous catalysis. LÄS MER

4. 3. Vibrational Spectroscopy of Surface Adsorbates on Metal Surfaces. Experiments and Calculations

   Författare :Ragnar K Ásmundsson; Kemisk fysik; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; ab initio electronic structure calculations; Fermi resonance; vibrational spectroscopy; Reflection absorption infrared spectroscopy; Fourier transform infrared spectroscopy; Cu 100 and W 110 single crystal surfaces; Physics; Fysik;

   Sammanfattning : This work deals with a detailed analysis of the vibrational spectra of methoxy (CH3O-) and ethoxy (CH3CH2O-) on W(110) and Cu(100) single crystal surfaces. By using theoretical ab initio quantum mechanical modeling, it is demonstrated that an unprecedented quantitative understanding of the vibrational frequencies of a surface adsorbate can be obtained. LÄS MER

5. 4. 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

7. 5. Understanding the interactions between vibrational modes and excited state relaxation in garnet structured phosphors

   Författare :Yuan-Chih Lin; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; free electron laser; thermal quenching.; luminescence; garnet; vibrational spectroscopy; neutron scattering; phosphor; light emitting diode;

   Sammanfattning : This thesis concerns investigations of the local structural environments and vibrational dynamics of the three garnet type oxide phosphors Ce3+-doped Y3Al5O12 (YAG:Ce3+), Ca3Sc2Si3O12 (CSS:Ce3+), and Sr3Y2Ge3O12 (SYG:Ce3+), which show promising optical properties as luminescent materials used in solid state white lighting technologies. The study focuses on a comprehensive analysis of the nature of the long-range vibrations (phonons) in terms of local atomic and molecular motions of the garnet structure, as well as their dependence on the nature of the garnet chemical composition, Ce3+ concentration and temperature. LÄS MER