The objectives of the proposed project are to advance the theoretical description of heavy elements and to apply the new methods to one group of such elements, the lanthanides. Heavy elements have many important applications in modern technologies due to their optical and magnetic properties. They are used as optical centers in active laser media, with the widely applied Nd:YAG laser being the most prominent example. Another application is the up- and down-conversion of light, a technique which can help to improve the efficiency of solar cells. This principle is currently also utilized in nanoparticles for bioimaging and therapy. Furthermore, organic compounds containing lanthanides are used in luminescent bioprobes for biological and medical applications such as cell imaging or the study of drug delivery processes. Recently, organic light emitting diodes based on these elements have gained interest. Concerning magnetic properties, solids containing lanthanides can have interesting magnetic features, as in the case of the well-known neodymium magnets. Their nanoscopic counterparts, known as “molecular magnets”, are attracting attention in recent years. In heavy elements two contributions are important: relativistic effects and correlation. While the importance of the special theory of relativity for the description of the movement of astronomical objects is commonly known, its importance for a correct description of heavy atoms is less obvious. However, relativistic effects are for example responsible for the color of gold or the melting point of mercury. Obviously, their importance for a correct treatment of atoms implicates also the necessity of relativistic approaches for molecules containing heavy elements. This can be achieved, at least in principle, by solving the Dirac equation, which is often avoided due to its complexity and the computational effort required to obtain a solution. The proposed project aims at the extension of a well-established approach to solve this equation, the relativistic coupled cluster method. In addition to its reliability, this method provides an accurate treatment of electron correlation, which is especially important for systems with many electrons. We will focus on systems with open shells, an electronic configuration which is typical for heavy elements with several orbitals of similar energy. The newly developed modules will be implemented in a relativistic quantum chemistry software package. In the return phase, they will be used to study selected, potentially interesting systems, which can be synthesized and investigated experimentally at the Institute of Experimental Physics at TU Graz.
|Effective start/end date
|1/02/21 → 14/02/22
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