Babyuk D. Time-dependent quantum methods in a study of adiabatic reactive dynamics of bimolecular collisions in gaseous phase

Objects of research: an elementary act of adiabatic bimolecular chemical reactions in the gas phase, the internal states of molecules. The purpose of research: within the quantum approach to develop software and implement new methods and efficient algorithms, followed by their application to study the adiabatic reaction dynamics of real and model systems. Research methods: the wave packet method, split-operator, grid methods, spectral method, discrete variable representation (DVR), Bohmian method, the quantum trajectory method (QTM), Monte Carlo method, hybrid method, covering function method (CFM). Theoretical and practical results: The QTM combined with developed in the dissertation the CFM makes possible to study quantum dynamics of bimolecular chemical reactions in which the total number of atoms exceeds four. Using the proposed reaction path Hamiltonian for systems with large number of degrees of freedom in which higher-order curvature close to zero, simplifies the study of reaction dynamics. The developed software package based on the combined method is suitable for studying the dynamics of any reacting system "atom - diatomic molecule" by incorporating in it the appropriate potential energy surface (PES) obtained from quantum-chemical calculations. The result may predict the possibility of the studied system in chemical laser. Novelty: For the first time the reaction cross sections for the exchange H + HCl = HCl + H, H + DCl = HCl + D and abstraction Н + HCl = НH + Cl, Н + DCl = НD + Cl reactions by means of quantum methods using the most accurate PES has been calculated. For the first time the true nature of the dynamical tunneling phenomenon, which appears in vibrational modes of some molecules. Using Bohmian approach to quantum theory proved that dynamic tunneling is only hidden type of barrier tunneling. An alternative formulation of the reaction path Hamiltonian, which differs from the traditional Hamiltonian by much simpler form of the kinetic energy operator, has been developed. For the first time the reaction probabilities have been calculated for the model system with 200 vibrational degrees of freedom. For the first time the possibility of application of pure QTM without any approximations to real reactive systems has been shown. Two original methods have been developed for coping with the node problem in QTM: hybrid method and covering function method. The second method found further application and development in the works of other researchers. Degree of implementation: Some software codes are implemented in course, diploma and master students' projects at the chemistry department of Chernivtsi National University.