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Showing 1 to 20 of 44 for “"lattice vibrations"”.
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Intrinsically Localized Lattice Vibrations in Crystalline Lattices
… [111] of the Sodium Iodide (NaI) crystalline lattice. The tendency for ILMs to form at a certain center-of-mass momentum ▁q and corresponding relative momentum vector ▁k is attributed to the van-Hove singularities condition in the non-interaction two-phonon density of states continuum. We …
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Scattering of Electrons by Lattice Vibrations in Crystals
Made available in DSpace on 2015-05-12T17:03:33Z (GMT). No. of bitstreams: 2 license.txt: 4848 bytes, checksum: 96035ab3f5e1c23cc7138a224ce498bd (MD5) 0018147.PDF: 3382658 bytes, checksum: cdd9f4253e5e533374f6611b68d03586 (MD5) Previous issue date: 1956
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Evaluation of Thermal Effects and Lattice Vibrations in Molecular Crystals
<p>The effect of temperature plays a large role in the behavior of many physical systems. While it is certainly the case that many effects of temperature can be observed macroscopically, they are often of molecular origin, and determining why these effects occur can provide insight into the nature …
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The attenuation of lattice vibrations by oscillations of independent and coupled dislocations
Submitted by Carolyn Mead (cmead2@illinois.edu) on 2011-06-27T14:43:10Z No. of bitstreams: 1 1980_kneezel.pdf: 7064208 bytes, checksum: 45091c0ec8874fba37383f65b6bb3048 (MD5)
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Investigating the Properties and Lattice Vibrations of Ordered and Disordered Crystalline Materials
… molecular crystals. Due to the complexities of lattice vibrations at such low frequencies, high-accuracy computational methods are necessary to interpret the experimental results. Such simulations are usually based on ideal, defect free, structures of crystals while experiments are performed on …
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Dynamics of lattice vibrations, molecular rotations and spins studied by terahertz spectroscopy
… responses of molecular dipole, spin, and lattice degrees of freedom in molecular and condensed-matter systems. We have developed several THz spectroscopy methods suitable for interrogating different material systems including THz pump-optical probe spectroscopy, THz time-domain electron …
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The excitation andn dynamics of coherent lattice vibrations in semimetals and narrow-gap semiconductors
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1994.
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Peculiar perovskites: Unraveling the unique optical response of hybrid organic-inorganic perovskites from first principles
… excited charge carriers, free-carriers, lattice vibrations, and atomic geometry influence the measured optical response of HOPs. First principles simulations provide a window to examine how these atomic-scale interactions contribute piece-by-piece to the measurable optical properties of …
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Ultrafast dynamics in complex molecular solids: Ultrafast imaging of laser ablation of PMMA and theory of mechanical energy flow in ultrahot crystalline naphthalene
… of energy between the internal molecular vibrations and the external modes or lattice vibrations. Two interesting examples involving this energy transfer are presented in this thesis. First, an ultrafast imaging apparatus is constructed and used to investigate spatially inhomogeneous …
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Self-Consistent Phonon Theory of Aperiodic Solids and Density Functional Theories of Freezing and Vitrification
… of the hard sphere crystal to an amorphous lattice. In doing so, we develop a theory of lattice vibrations in amorphous materials via a perturbation theory around the Einstein oscillator approximation. This development is analogous to the mean spherical model description of electronic …
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Photoinduced phase transitions studied by femtosecond single-shot spectroscopy
… instrument, ultrafast dynamics of coherent lattice vibrations and photo-induced phase transitions were examined in two different systems. Ultrafast dynamics such as coherent lattice vibrations and bond softening were investigated for Bi thin films and bulk single crystals. Depending on the …
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Non-equilibrium energy transfer and phase change during intense picosecond laser-metal interactions
… energy coupling between electrons and the lattice, and energy transport by diffusion of electrons and lattice vibrations. During picosecond laser irradiation of metal films, electrons and the lattice are not in thermal equilibrium. On the other hand, rapid laser heating produces a large …
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An investigation by electron paramagnetic resonance of the Jahn-Teller effect in LiNbO₃¿:Cu²+
… of C3) as Cu+. As a result of coupling to lattice vibrations, the ground manifold consists of a doubly degenerate vibronic ground state and a nearby singlet. An affective Hamiltonian that Includes the strain, Zeeman, and hyperflne interactions is formulated for ground manifolds of* l) …
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n-type silicon-germanium based terahertz quantum cascade lasers
… imperfections and interactions with phonons (lattice vibrations) are developed and used to predict the electron distribution, current density and gain in a range of device designs. The effect of nonabrupt interface geometries is investigated and the effect of intervalley mixing upon the …
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Computational Methodologies for the Simulation and Analysis of Low-frequency Vibrations in Molecular Crystals
… methodologies for simulating and analyzing the lattice vibrations of molecular crystals such as torsions and translations. The developed computational approaches utilize solid-state density functional theory to account for the periodic nature of a molecular crystal and include careful …
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The Role of Disorder in the Charge Dissociation and Recombination Processes of Organic Photovoltaic Materials
… simplifies complicated molecular structures to a lattice system, while taking into account electron and hole Coulombic and exchange interactions, lattice vibrations, and electron-phonon couplings. In addition, we examine the role of band-width and interfacial driving forces in determining the …
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Polaritonics : an intermediate regime between electronics and photonics
… carried by an admixture of electromagnetic and lattice vibrational waves known as phonon-polaritons, rather than currents or photons. Impulsive stimulated Raman scattering (ISRS) is employed for phonon-polariton generation, whereby lattice vibrations are driven by optical femtosecond laser …
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Modeling nanoscale transport phenomena: Implications for the continuum
… due to both the ballistic propagation of lattice vibrations in small confined dimensions and a diffusive behavior that is observed at larger length scales. Our simulations determine the length dependence of thermal conductivity for these cases as well as effects of isotope substitution in …
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EXPERIMENTAL AND COMPUTATIONAL ANALYSIS OF RELATIVE ENERGETIC STABILITIES OF CRYSTALLINE ANHYDROUS POLYMORPHS AND PSEUDOPOLYMORPHS
… (THz-TDS). Terahertz spectroscopy of the lattice vibrations offers a sensitive probe of solid-state interactions and serves as a rigorous benchmark for testing the quality of the applied theoretical methods. Vibrational simulations of different polymorphic forms are also useful for …
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Phonon Behaviour at Advanced Material Interfaces using Electron Energy Loss Spectroscopy
… electron microscopes (STEM) enable the study of lattice vibrations (phonons) with nanoscale spatial resolution using electron energy loss spectroscopy (EELS). Probing phonons at this spatial resolution provides access to vibrational properties associated with structural features in which the …
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