This work includes a study of the propene epoxidation by hydrogen peroxide in different types of environment, from the gas phase to the TS-1. We calculated the energy and activation barrier of the reaction. The barrier proved to be very sensitive to environment. Even a single water molecule has a notable catalytic effect, and so do the explicit zeolite environment and the electric field. An attempt has been made to built QM/MM model of TS-1, however this model did not yield adequate results due improper charge embedding of the MM charges into the QM wavefunction.
COBISS.SI-ID: 4121370
We studied the Ti location problem in the TS-1 catalyst by the periodical HF method. We modeled the 12 Ti-substitution isomers and compared their energies, also as function of symmetry constraints imposed by the space group. The energy range of the isomers was found to be narrow (about 5 kcal/mol) and decreasing on the decreasing Ti content. Due to small energy differences between the isomers, one cannot rule out the possibility that the Ti-siting is entirely random, or governed by entropic or kinetic effects.
COBISS.SI-ID: 4076826
This work includes a spectroscopic and computational study of crystalline picolinic acid N-oxide. We simulated the vibrational spectrum of the O-H moiety of the H-bond. We propose a novel approach for the evaluation of contours of vibrational bands. The approach is based on dynamical sampling of the proton potential function, acquired from the snapshots of the MD simulation. Nuclear quantum effects have proved to be crucial for a reasonable reproduction of the experimental contour of the OH stretching band.
COBISS.SI-ID: 3743002
This paper includes a crystallographic and computational study of the structure of tetraacetylethane (TAE). The molecule is asymmetric despite the fact that it is chemically symmetric. In our quest for the driving force that renders the TAE structure to be asymmetric, we performed a CPMD simulation and found that the main origin of the asymmetry is in the coupling between the torsion of methyl groups and the longitudinal proton motion. Since the methyl rotations are hindered due to weak C-H…O interactions within the crystal structure, the resulting proton potential is no longer symmetric.
COBISS.SI-ID: 3975706