Search results for "kvanttikemia"
showing 4 items of 14 documents
Theoretical and computational studies of magnetic anisotropy and exchange coupling in molecular systems
2018
The field of molecular magnetism studies the magnetic properties of molecular systems as opposed to conventional metal-based magnets. The high chemical modifiability of the constituting molecules makes such materials highly versatile, and the small size of the building blocks leads to the rise of various quantum mechanical phenomena, such as tunneling and entanglement. These phenomena can then be further utilized in the construction of nanoscale quantum devices. This dissertation describes computational and theoretical studies in the field of molecular magnetism using state-of-the-art quantum chemical methods based on ab initio multireference approaches and broken symmetry density functional t…
Protonation of the Biliverdin IXα Chromophore in the Red and Far-Red Photoactive States of Bacteriophytochrome
2019
The tetrapyrrole chromophore biliverdin IXα (BV) in the bacteriophytochrome from Deinococcus radiodurans (DrBphP) is usually assumed to be fully protonated, but this assumption has not been systematically validated by experiments or extensive computations. Here, we use force field molecular dynamics simulations and quantum mechanics/molecular mechanics calculations with density functional theory and XMCQDPT2 methods to investigate the effect of the five most probable protonation forms of BV on structural stability, binding pocket interactions, and absorption spectra in the two photochromic states of DrBphP. While agreement with X-ray structural data and measured UV/vis spectra suggest that …
High-Level Ab Initio Predictions of Thermochemical Properties of Organosilicon Species: Critical Evaluation of Experimental Data and a Reliable Bench…
2022
A high-level composite quantum chemical method, W1X-1, is used herein to calculate the gas-phase standard enthalpy of formation, entropy, and heat capacity of 159 organosilicon compounds. The results set a new benchmark in the field that allows, for the first time, an in-depth assessment of existing experimental data on standard enthalpies of formation, enabling the identification of important trends and possible outliers. The calculated thermochemical data are used to determine Benson group additivity contributions for 60 Benson groups and group pairs involving silicon. These values allow fast and accurate estimation of thermochemical parameters of organosilicon compounds of varying comple…
Grand Canonical Rate Theory for Electrochemical and Electrocatalytic Systems I : General Formulation and Proton-coupled Electron Transfer Reactions
2020
Electrochemical interfaces present a serious challenge for atomistic modelling. Electrochemical thermodynamics are naturally addressed within the grand canonical ensemble (GCE) but the lack of a fixed potential rate theory impedes fundamental understanding and computation of electrochemical rate constants. Herein, a generally valid electrochemical rate theory is developed by extending equilibrium canonical rate theory to the GCE. The extension provides a rigorous framework for addressing classical reactions, nuclear tunneling and other quantum effects, non-adiabaticity etc. from a single unified theoretical framework. The rate expressions can be parametrized directly with self-consistent GC…