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Showing 1 to 18 of 18 for “"Many body perturbation theory"”.
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Finite-temperature many-body perturbation theory for electrons
Correct benchmark perturbation corrections, up to third order, to the electronic internal energy, chemical potential, grand potential, and entropy of an ideal gas of noninteracting, identical molecules in a wide range of temperature were determined numerically as the λ-derivatives of the respective …
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Ab initio Hartree-Fock and many body perturbation theory calculation of the energies of the excited states of some materials
… Unrestricted Hartree-Fock technique augmented by many body perturbation theory techniques and symmetry projection methods in the study of the energies of the excited states of atomic, molecular and solid state systems is investigated. A perturbation method for finding relativistic corrections to …
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Optimization Problems in Hilbert Space with POSS Complexes.
… in classical physics, we derive the Hartree-Fock theory from canonical quantization. Following a development of density functional theory, many-body perturbation theory, and other techniques of computational condensed matter physics, we perform a systematic study of metal-polyhydride impurities in …
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Diagrammatic many-body methods for anharmonic molecular vibrational properties
Diagrammatic many-body methods for computing the energies and other properties of anharmonic vibrations have been developed based on the Dyson equation formalism for the single-particle vibrational Green's function and the many-body perturbation theory for the total zero-point energy. Unlike …
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Real-Time Dynamics of Electrons and Phonons from First Principles
… effects. In addition, a first-principles theory of coherent phonon damping is developed using many-body perturbation theory, demonstrating that phonon frequency renormalization and decay are governed by the phonon self-energy arising from electron–phonon and phonon–phonon interactions. …
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Physics in Screening Environments
… we show second-order Green'sfunction results and many body perturbation theory results of second order.A self-contained derivation of all necessary equations has been included. Theaccuracy of the implementation of the method is established by comparingstandard unscreened results for various atoms …
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Peculiar perovskites: Unraveling the unique optical response of hybrid organic-inorganic perovskites from first principles
… optical calculations based on density functional theory and many-body perturbation theory to determine how the optical response and excitonic properties of HOPs and LHOPs are influenced by the presence of free-carriers, polar lattice vibrations, and layer stoichiometry. In order to describe polar …
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Computational modeling of defects in nanoscale device materials
… in this thesis, consisting of density functional theory (DFT) supplemented with many body perturbation theory (MBPT) methods, of native defects in bulk and slab models of In0.53Ga0.47As. The latter consist of (100) - oriented surfaces passivated with A12O3. Our results indicate that the …
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Monte Carlo explicitly correlated methods
… is Monte Carlo (MC). The stochastic second-order many-body perturbation theory, or the MC-MP2-F12 method, was developed for highly parallel evaluation of second-order many-body perturbation theory (MP2) energies near the complete basis set (CBS) limit. Single molecule energies were on average …
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First principles modelling of tunnel field-effect transistors based on heterojunctions of strained Germanium/InGaAs alloys
… of the Ge and GaAs band gaps, calculated at Many-Body Perturbation Theory (MBPT) level, is added to the potential line-up of a supercell structure containing the Ge/GaAs interface, calculated using Density Functional Theory (DFT). It was studied how the band alignment is affected by the …
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DESCRIPTION OF POLARONS IN LAYERED TRANSITION METAL OXIDES USING THE r2SCAN DENSITY FUNCTIONAL WITH FULLY NONLOCAL CORRECTIONS AND EFFECT OF STRAIN ON THE BAND GAP OF MONOLAYER MOLYBDENUM DISULFIDE
… ratio of 0.44. We conducted density functional theory (DFT) calculations on a free-standing MoS2 monolayer using the generalized gradient approximation (GGA) PBE, the hybrid functional HSE06, and many-body perturbation theory with the GW approximation using PBE wavefunctions (G0W0@PBE). Our …
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Optical and electronic properties of defective semiconductors from first principles calculations
… approaches based on density functional theory (DFT) and many-body perturbation theory (MBPT) to quantitatively describe trap state energies and optical excitation spectra of defective bulk gallium nitride (GaN) and monolayer germanium selenide (GeSe). GaN is a technologically important …
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Ab initio modelling of photoinduced electron dynamics in nanostructures
… the semiconducting TMD (i.e. density functional theory (DFT) and many-body perturbation theory) may not be applied to the full TMD-MNP structure as the MNP is often on a much larger scale than the semiconductor rendering the ab initio methods infeasible.<br/><br/>In this thesis, we develop a …
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Computational investigation on polycyclic aromatic hydrocarbons in the molecular and solid phases
… We used all-electrons density functional theory(DFT)and time- dependent DFT(TDDFT)to quantify the effects of morphology and chemical modifications ondifferent physical observables, namely electron affinity,ionization energy,quasi-particleenergy gap,optical absorption,excitonbindingenergy, …
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Exchange-Correlation Kernels Within Time-Dependent Density Functional Theory For Ground-State and Excited-State Properties
… Therefore, it must be modeled either using many-body perturbation theory or by satisfying the exact constraints for various prototype systems such as the paradigm uniform electron gas (UEG). The random phase approximation (RPA) neglects the kernel, therefore, fails to provide the accurate …
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Theoretical study of nanocrystals and other functional nanostructures of silicon and alternative group - 14 elements
… of this work is based in density functional theory (DFT), both ground state and time-depended, using in most cases the hybrid functional of Becke, Lee, Parr and Yang (B3LYP), and in several places the PBE and PBE0 functionals. A limited number of calculations was performed with post SCF …
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Advancements in Monte Carlo many body methods
Many-body methods are one of the most powerful tools that may be brought to bear to solve the electronic structure problem. While both of the following theories provide a complete path to obtain any quantity, many-body perturbation theory is principally used to provide molecular energies, while …
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Electronic, Optical, and Thermal Properties of Reduced-Dimensional Semiconductors
… an atomic scale yield promising applications for many fields including nanoelectronics, nanobiotechnology, environments, and renewable energy. Because of the unusual quantum confinement and enhanced surface effect of reduced-dimensional materials, traditional empirical models suffer from necessary …