|
|
Aplication of explicitly correlated multi-reference coupled cluster methods
Lang, Jakub ; Pittner, Jiří (advisor) ; Fišer, Jiří (referee)
Nowdays, coupled cluster method belongs to one of the most used quantum chemical methods. However, the single-reference coupled cluster methods are not able to describe systems where the static correlation have an important role. Multireference coupled cluster methods developed in our group can describe both static and dy- namic correlation and can be used for problematic systems. Together with explicitly correlated wavefunction, which can properly describe the electronic cusp and speed up the convergence to the complete ba- sis set limit, they are able to calculate computationally demanding diradicals. Multireference CC calculations of tetramethylenethane have been perforemd and the performance of explicitly correlated version is discussed. Calculations of the isomerization of bicyclobu- tane using the multireference approach are presented as well. 1
|
|
| |
|
|
Nonlocal correlation in density functional theory
Hermann, Jan ; Bludský, Ota (advisor) ; Fišer, Jiří (referee)
e van der Waals (vdW) interactions, or dispersion forces, are crucial in many chem- ical, physical and biological processes and received much attention from developers of density functional theory (DFT) methods. e most popular non-empirical DFT method for treating vdW interactions is the vdW density functional by Dion et al. (vdW-DF). Despite its success, vdW-DF is not accurate enough for many chemical applications. Here, we investigate two possible ways how to improve its accuracy. First, we reoptimize the only weakly speci ed parameter of vdW-DF for several semi-local functionals. On the S benchmark database set, we nd that revPBE is the best performer, decreasing the error from . % to . %. Second, a system-speci c but very accurate (∼ . kcal/mol) DFT correction scheme is proposed for precise calcula- tions of adsorbent−adsorbate interactions by combining vdW-DF and the empirical DFT/CC correction scheme. e new approach is applied to small molecules (CH , CO , H , H O, N ) interacting with a quartz surface and a lamella of UTL zeolite. e very high accuracy of the new scheme and its relatively easy use and numerical stability compared to the earlier DFT/CC scheme o er a straightforward solution for obtaining reliable predictions of adsorption energies.
|
|
| |
|
|
Theoretical investigation of water-zeolite interactions under steaming conditions
Benešová, Tereza ; Heard, Christopher James (advisor) ; Fišer, Jiří (referee)
The thesis is focused on theoretical study of hydrolysis and isotopic oxygen exchange in zeolite chabazite under steaming conditions. The theoretical study was performed by the methods of computational chemistry, namely density functional theory. Reactions of water with zeolites were investigated within the periodic model with chabazite supercell consisting of 36 Si/Al tetrahedra. Reactivity was investigated for one or two water molecules corresponding to the conditions relevant to high-temperature steaming. Relevant mechanisms of isotopic oxygen exchange were found and their competitiveness with hydrolysis was discussed.
|
|
| |
|
|
Multireference State-Specific Mukherjee's Coupled Cluster Method with Non-iterative Triexcitations.
Bhaskaran Nair, Kiran ; Pittner, Jiří (advisor) ; Noga, Jozef (referee) ; Fišer, Jiří (referee)
The multireference (MR) generalization of coupled cluster (CC) theory aims to describe both the static and the dynamic correlation accurately, as the standard CC method (at lower truncation levels) generally does not perform well when quasidegenerate boundary orbitals are encountered. The most promising among the MR Hilbert-space methods seems to be the state-specific MR Mukherjee's CC (MkCC) method, formulated by Mukherjee et al. [J. Chem. Phys. 110, 6171 (1999)], due to its rigorous size-extensivity and insensitivity to the intruder state problem. The main goal of this work was to include connected triples in the MkCC method. As the cost of the iterative triples limits its application, the main focus was on including triples non-iteratively. Two perturbative triples methods, namely MkCCSD(Tn) and MkCCSD(Tu) have thus been developed. For studying their accuracy, iterative triples methods (MkCCSDT and MkCCSDT-n) were also developed using the "linked" formulation. All these methods and an uncoupled version of MkCC (uMkCC) were implemented in the ACES II program. The assessment of these methods was performed on the O2, cyclobutadiene, methylene diradical, twisted ethylene, F2, BeH2 and tetramethyleneethane (TME) molecules. All these studies show that the inclusion of triexcitations improves the...
|
|
|
Analogy of social information systems and information systems of living organisms in selected texts
Fišer, Jiří ; Fonferová, Ľudmila (advisor) ; Slámová, Hana (referee)
In the first half, the work is about human society information systems. It tries to find an origin of the information in the society, describes forms of the information and tries to explain causes for communication. Later it describes main attributes of the system itself. From mentioned facts the work then figures out an idea about new division of information systems based on the purpouse of a system. The next part concerns information structures present in the body of plants and plant neurobilology. Then the work question the relationship between the information science and the cognitive science. Later the woork tries to work out some global charakteristics of plant information structures. In the last part work discuss the basic funcions of the human brain and late discoveries in glia cells field. Conclussion of the whole work follows. Keywords *information system *information communication *living organisms *plant neurobiology *consciousness *glia *analogies
|
|
| |
|
|
The Analysis of Information Flows Management within the Microenvironment of Krajská Vědecká Knihovna v Liberci : a Case Study
Fišer, Jiří ; Slámová, Hana (advisor) ; Papík, Richard (referee)
Informetrics study the information flow as a pure information phenomenon. However what are the practical applications of this problem? Information flow can be understood, investigated and managed from different points of view. The most practical one is management approach combined with intuitive analogy. Water flow parallel appears suitable. A conceptual model can be propounded upon this foundation and then used for better illustration of information flow function and key parts. Finally, a good amount of instruments and management methods can be used to manage information flows. So in chosen organization the current state of information flows and contemporary methods of its management are investigated in order to compare the theory and the practice. Concrete suggestions and statements about information flow management are deduced afterwards This paper illustrate possibilities of usage of information flow management in practice. Keywords information flow management - methods of information flow management - information flow model - practical aplications - case study - analogy - induction - Regional research library in Liberec
|
guest ::
RSS feed.