Sökning: "quantum mechanics molecular mechanics"

Visar resultat 1 - 5 av 60 avhandlingar innehållade orden quantum mechanics molecular mechanics.

1. 1. Fingerprints of light-induced molecular transients : from quantum chemical models of ultrafast x-ray spectroscopy

   Författare :Jesper Norell; Michael Odelius; Sang-Kil Son; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; time-resolved x-ray spectroscopy; quantum chemistry; electronic structure; multi-configurational self-consistent field; density functional theory; molecular dynamics; Born-Oppenheimer dynamics; non-adiabatic dynamics; proton-transfer; charge-transfer; solvatization; Dyson orbital; teoretisk fysik; Theoretical Physics;

   Sammanfattning : Absorption of sunlight generates renewable electricity and powers the growth of plants, but also causes severe damage both to synthetic materials and biological tissue. The wildly varying outcomes of these light-induced processes are ultimately determined by much slighter differences in their underlying reaction pathways, induced by the transient properties of short-lived and miniscule molecules; a powerful approach to their detection and characterization is offered by ultrafast x-ray spectroscopy, with identification of spectral fingerprints and further guidance from quantum chemical models. LÄS MER

3. 2. Algorithms for Molecular Dynamics Simulations

   Författare :Fredrik Hedman; Aatto Laaksonen; Tom Darden; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; molecular dynamics; MD; first principles molecular dynamics; quantum mechanics; liquid water; parallel algorithm; data parallel; MPI; Coulombic interaction; Ewald summation; nonuniform fast Fourier transform; FFT; FFTW; NFFT; ENUF; Physical chemistry; Fysikalisk kemi;

   Sammanfattning : Methods for performing large-scale parallel Molecular Dynamics(MD) simulations are investigated. A perspective on the field of parallel MD simulations is given. Hardware and software aspects are characterized and the interplay between the two is briefly discussed. LÄS MER

4. 3. Quantum Dynamics of Molecular Systems and Guided Matter Waves

   Författare :Mauritz Andersson; Tamar Seideman; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Quantum chemistry; quantum dynamics; femtosecond spectroscopy; photoelectron spectroscopy; resonances; nonadiabatic interaction; coherent state representation; adaptive numerical method; Kvantkemi; Quantum chemistry; Kvantkemi; Quantum Chemistry; kvantkemi;

   Sammanfattning : Quantum dynamics is the study of time-dependent phenomena in fundamental processes of atomic and molecular systems. This thesis focuses on systems where nature reveals its quantum aspect; e.g. in vibrational resonance structures, in wave packet revivals and in matter wave interferometry. LÄS MER

5. 4. Probing Magnetism at the Atomic Scale:  Non-Equilibrium Statistical Mechanics Theoretical Treatise

   Författare :Juan David Vasquez Jaramillo; Jonas Fransson; Rosa Lopez; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Non-Equilibrium Statistical Mechanics; Magnetism; Quantum Optics; Quantum Coherence; RKKY; Colciencias; Equation of Motion; Jauho-Meir-Wingreen Formalism; Physics with spec. in Atomic; Molecular and Condensed Matter Physics; Fysik med inriktning mot atom- molekyl- och kondenserande materiens fysik; Physics with specialization in Quantum Chemistry; Fysik med inriktning mot kvantkemi; Physics and Astronomy specializing in Theoretical Physics; Fysik och astronomi med inriktning mot teoretisk fysik;

   Sammanfattning : Here, I present a theoretical study, based on non-equilibrium quantum statistical mechanics and on the non-equilibrium extension to the RKKY intveraction,where I investigate the emergence of magnetism at the atomic scale in adsorbed molecular complexes hosting localized spin moments, at the stake of being probed with scanning tunneling microscopy tip, and being driven by a temperature gradient and gated by an electric field. The scanning tunneling microscopy set up is modeled as a molecular junction with a magnetic molecule embedded within it, where the molecule consists in a set of electronic levels resembling the typical s-p orbitals of a metal hydride or an organometal, and a localized spin moment resembling the magnetic unit hosted by the latter and former type of molecules mentioned. LÄS MER

7. 5. Coherent Interactions in Rare-Earth-Ion-Doped Crystals for Applications in Quantum Information Science

   Författare :Mattias Nilsson; Atomfysik; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; quantum optics; relaxation; magnetic resonance; supraconductors; magnetic and optical properties; electrical; Condensed matter:electronic structure; Atom- och molekylärfysik; optical information processing; coherence in solids; Atomic and molecular physics; rare-earth-ion-doped crystals; magnetisk resonans; spektroskopi; supraledare; magnetiska och optiska ; egenskaper elektriska; Kondenserade materiens egenskaper:elektronstruktur; spectroscopy; quantum information;

   Sammanfattning : This thesis describes investigations of the use of cryogenically cooled rare-earth-ion-doped crystals for quantum information processing and quantum optics. Several aspects of the coherent interaction between light and rare-earth ions in solids are addressed. Quantum information science has given physicists new views of quantum mechanics. LÄS MER