### Main research and teaching activities

**Research activity** of the team and its PhD students is oriented to the development of quantum chemistry methods for accurate calculations of molecular properties. We paid particular attention to accurate calculations of nonlinear electric properties, chemical reactivity, intermolecular interactions, ionization potentials and electron affinities, chemistry of the atmosphere, etc. including calculations of properties of radicals and molecules in excited states. Important area of interest concerns relativistic effects on molecular properties.

**Substattial effort** is focused on further development of methods for efficient treatment of the electron correlation problem with high and controlled accuracy. Members of the team have contributed to the development of Coupled Cluster (CC) methods, particularly to the CCSD(T) method, which is occasionally called the “golden standard” of quantum chemistry, and to different variants of approximate and full iterative CCSDT method. Along with the development of highly accurate ab-initio approaches, more pragmatic methods of molecular modeling of larger systems, up to modeling of multi-molecular systems based on the principles of statistical mechanics have been the area of interest of the group.

**Recently implemented CCSD(T) method** utilizes the reduced optimized virtual orbital space (OVOS). We obtained most results using the functional that optimizes the overlap between the first-order correlated wave function in the full virtual space and the reduced space, respectively. Truncating the virtual space to, say, one halve of the original full space, the computer time for CCSD(T) calculation can be reduced by order of magnitude. We have demonstrated the potential of the method in calculations of a series of molecular properties, reaction energies, intermolecular interactions, etc. Our CCSD(T) computer programs utilize parallelism as well as Choleski decomposition, which allow efficient treatment of four index integrals and amplitudes.

**Particularly interesting applications ** are:
computer design of experimentally unknown molecules and molecular clusters,
computer modelling of chemical equilibria, rate processes and catalysis in the gas-phase and solution for the cases not easily
amenable to experiment.
The scope of applications is extended also to excited states, non-covalent interactions with the specific aim to biomolecules and calculation of various molecular properties.

**Research team**
involves three full professors (Ivan Černušák, Vladimír Kellö and Miroslav Urban,),
three associate professors (Pavel Neogrády, Tomáš Bučko and Michal Pitoňák) and one assistant professor
(Lukáš F. Pašteka).
Five up to eight graduate students/postdocs usually participate on scientific projects.