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Showing 1 to 14 of 14 for “"explicitly correlated"”.
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Monte Carlo explicitly correlated methods
… of instantaneous correlation through expensive correlated methods. The methods that have been developed to account for the incompleteness of the basis set, the R12/F12 methods, create high dimensional integrals that need to be separated with the resolution of the identity, are limited in their …
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Explicitly Correlated Methods for Large Molecular Systems
… the second problem is alleviated by the use of explicitly correlated R12/F12 methods. Since R12/F12 methods are central to this work, we start by reviewing their modern formulation. Next, we present the explicitly correlated second-order Mo ller-Plesset (MP2-F12) method in which all nontrivial …
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Accurate Calculations of Molecular Properties with Explicitly Correlated Methods
… function at short inter-electronic distances. Explicitly correlated methods overcome this basis set problem by including the inter-electronic distances (rij) explicitly in wave function expansions. Here, the origin of the basis set problem of conventional wave function methods is reviewed, and …
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Explicitly correlated Green's function methods for calculating electron binding energies
… set incompleteness error. An energy-dependent explicitly correlated (F12) formalism for Green's function is presented that achieves faster convergence to the basis set limit. The renormalized second-order Green's function method (NR2-F12) scales as iterative N^5 where N is the system size. …
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Exploration and Optimization of the One- and Many-particle Basis Sets in Modern Explicitly Correlated Electronic Structure
… either basis set extrapolation or the use of explicitly correlated wavefunctions that address the deficiencies of standard determinantal expansions at short interelectron distances in order to yield accurate electron correlation energies in molecules. Practical and robust explicitly correlated …
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Development of explicitly correlated and many-body diagrammatic techniques for the investigation of electron-hole correlation in nanomaterials
<p>The focus of this work is to develop theoretical methods that will accurately describe electron-electron and electron-hole correlation in nanoparticles using many-body diagrammatic techniques. Diagrammatic representation is a more complex representation of quantum mechanics, however, it becomes …
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Development and Application of Explicitly Correlated Wave Function Based Methods for the Investigation of Optical Properties of Semiconductor Nanomaterials
… theoretical method which is called electron-hole explicitly correlated Hartee-Fock (eh-XCHF). It is a variational method for solving the electron-hole</p> <p>Schrodinger equation and has been used in this work to study electron-hole interaction in semiconductor quantum dots. The method was …
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Very Accurate Quantum Mechanical Non-Relativistic Spectra Calculations of Small Atoms & Molecules Employing All-Particle Explicitly Correlated Gaussian Basis Functions
… the non-BO method and the BO approximation using explicitly correlated Gaussian (ECG) basis functions. The physical systems studied in this dissertation are the atomic elements with Z < 7 (although the discussion is not limited to these) and diatomic molecules such as H₂⁺ and H₂ including nuclear …
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Theoretical investigation of the quantum-confined Stark effect
… dissertation are the systematic development of explicitly correlated electron-hole wave function based methods and the application of these methods to chemical systems with an</p> <p>emphasis on nanoparticles.</p> <p>The understanding of the basic physics of excited electronic states is an …
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Electron-proton nonadiabaticity: characterization and development of non-Born-Oppenheimer electronic structure methods
… Subsequent efforts focused on the development of explicitly correlated NEO approaches which, although accurate, were too computationally intractable to be practical for the study of PCET systems. In this dissertation, we describe two approaches to develop tractable NEO methods. Firstly, we …
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Explicit Feature Relation and Implicit Feature Correlation Knowledge in Semantic Memory
… tasks. It is concluded that both implicitly and explicitly correlated feature pairs influence conceptual computations.
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On the Nature of Weak Intermolecular Forces: a First Principles Approach to Hydrogen Bonding and Pi-Type Interactions
… crystal structures are investigated with explicitly correlated methods. In Chapter 5, electronic structure computations are used to systematically examine nine small hydrocarbon molecules interacting with water. The structures, energetics and nature of hydrocarbon/water interactions in 30 …
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Coupled-Cluster Methods for Large Molecular Systems Through Massive Parallelism and Reduced-Scaling Approaches
Accurate correlated electronic structure methods involve a significant amount of computations and can be only employed to small molecular systems. For example, the coupled-cluster singles, doubles, and perturbative triples model (CCSD(T)), which is known as the ``gold standard" of quantum chemistry …
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Efficient automated implementation of higher-order many-body methods in quantum chemistry
To follow up on the unexpectedly-good performance of coupled-cluster models with approx- imate inclusion of 3-body clusters [J. Chem. Phys. 151, 064102 (2019)] we performed a more complete assessment of the 3CC method [J. Chem. Phys. 125, 204105 (2006)] for accurate computational thermochemistry in …