Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 9 of 9 for “"Nuclear Quantum Effects"”.
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The Role of Nuclear Quantum Effects in Supercooled Water and Amorphous Ice
… classical molecular dynamics simulations where nuclear quantum effects (NQE) are neglected. This can be troublesome because water is a light molecule and NQE are known to influence the structural and dynamic properties of water even at ambient conditions. For example, in H<sub>2</sub>O and …
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Development of non-born-Oppenheimer methods for ground and excited state molecular properties
The nuclear-electronic orbital (NEO) method is a multicomponent approach that allows the quantum mechanical treatment of electrons and specified protons on the same quantum mechanical level. NEO does not make the Born-Oppenheimber approximation between electrons and select protons, and therefore …
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Approximations to Matsubara Dynamics for Vibrational Spectra
… purpose of accurately and efficiently including nuclear quantum effects in vibrational spectra, with a particular focus on anharmonic dynamics and non-fundamental transitions. All the methods investigated are approximations to Matsubara dynamics, which is a rigorous theoretical framework that …
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Charge Density Waves and Superconductivity in Rare Earth Compounds from First Principles
… tools for this purpose and find that the effects of strong correlation (captured with DFT+U simulations) has a nontrivial effect on the susceptibility of these materials to structural distortions. In doped rare earth trihydrides, nuclear quantum effects are found to stabilize the system …
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Semiclassical Approaches to Complex Chemical Simulation in Real Time
… offers a pedagogically rich connection between quantum and classical perspectives of nature, and, furthermore, is a promising approach to incorporating quantum effects into molecular dynamics simulations. However, a variety of numerical challenges associated with SC methods, such as the …
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Towards routine modelling of condensed phases with the accuracy of quantum Diffusion Monte Carlo
… surface (PES), and (ii) a fully anharmonic, quantum statistical treatment of ionic motion. Despite recent advancements addressing these challenges, routine and economically viable modelling of molecular crystals with quantitative agreement to experiments remains elusive. This thesis …
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An Analysis of Three Path-Integral Based Approximations to Quantum Dynamics
… dynamics of the atomic nuclei need to be treated quantum mechanically. In this thesis we analyse three path-integral based approximations for computing quantum time-correlation functions: constant-uncertainty molecular dynamics (CUMD), the fitted harmonic approximation (FHA) and windowed centroid …
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Electron-proton nonadiabaticity: characterization and development of non-Born-Oppenheimer electronic structure methods
Nuclear quantum effects such as zero-point energy and hydrogen tunneling play an important role in a wide variety of chemical reactions. Moreover, non-Born-Oppenheimer effects are important in reactions such as proton-coupled electron transfer (PCET), which are integral to various electrocatalytic …
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Ab initio investigations of low Z materials under extreme conditions
… systems have to treat electron correlation and nuclear quantum effects approximately. In hydrogen and lithium, the errors introduced by these approximations are comparable to the enthalpy differences between competing phases, giving inaccurate phase boundaries. We believe that several …