Advanced Electronic Structure Methods Group
Team leader: dr hab. Michał Lesiuk, prof. ucz.
Team leader’s e-mail address: m.lesiuk@uw.edu.pl
Brief description of the research topic:
The Advanced Electronic Structure Methods Group is located at the Faculty of Chemistry, University of Warsaw, Poland. We are a group of theoretical and computational chemists and physicists focused on developing new quantum chemistry methods and applying them to solving various scientific problems. In particular, we perform research in the following areas:
New organic materials for light-emitting diodes. An organic light-emitting diode (OLED) is a device which emits light in response to an electric current and where the electroluminescent layer comprises an organic compound responsible for the emission. The applications of OLEDs are widespread and nowadays they are found in numerous pieces of modern technology, such as mobile phones and digital cameras, among others. Recently, it has been found that the heptazine molecule, as well its substituted derivatives, exhibits a negative singlet-triplet gap, i.e. the first excited singlet state has lower energy than the first excited triplet state. This unique property, contradicing the near-universal Hund’s rule, enables to harvest the energy from the triplet excitation channel and increase the quantum efficiency of the OLED devices. Our work focuses on development of cost-effective quantum chemistry methods for excited state which are able to describe the singlet-triplet inversion with quantitative accuracy. For this purpose we combine the rank-reduced coupled-cluster methods, embedding techniques and density functional theory.
Theoretical modelling of proton-matter interactions. Accurate description of interactions between high-energy protons (as well as heavier atomic nuclei) and matter is important in many applications, in particular in radiation therapy used for treatment of various types of cancer. We are developing new electronic structure methods which are able to model such interactions, both in the perturbative regime and within explicitly time-dependent framework. These methods are not limited to description of small systems and are aimed at calculations for basic molecular structures building human tissues. Theoretical description of proton-induced processes is expected to provide insight into details of such interactions and chemical transformations induced by high-energy beams.
Accurate ab initio calculations for small systems. Accurate first-principles calculations for small atomic and molecular systems are a constant challenge for theoretical and computational chemists. To match the accuracy standards of modern experimental techniques, new electronic structure methods have to be developed. Our work in this area in largely inspired by recent advances in metrology, in particular by the development and refinement of experimental techniques such as dielectric constant gas thermometry or refrative index gas thermometry. These methods establish a new standard for measuring fundamental quantities such as pressure, and will replace older standards based on mechanical devices. However, gas thermometry experiments require a significant theoretical input. In particular, to take into account deviations from the ideal gas model, the so-called pressure and dielectric virial coefficients are needed. Our work concentrates on developing new theoretical methods to compute this quantities and on applying them to systems relevant for the experimentalists.