Broken symmetries in relativistic quantum chemistry

forthcoming

BRUNCH is a fundamental project that will provide an entirely new theoretical framework and develop an ambitious methodological toolbox to tackle the current challenges of molecular magnetism. f-ions-based molecular magnets and subsequent multifunctional materials are on the way to offering the building blocks for tomorrow's technologies, such as quantum computing and spintronics. Most of their appealing features originate from relativistic effects, which are huge in lanthanide and actinide-based complexes. Whilst theoretical chemistry is known to have provided a critical understanding of magnetic phenomena, it faces the reality of increasing complexity in terms of the size and diversity of the physicochemical properties of interest. BRUNCH aims to make density functional theory (DFT) a new standard in molecular magnetism, offering unprecedented access to the computation of magnetic and luminescence properties. Despite its hegemony in chemistry, DFT cannot properly describe magnetic systems, and their study relies on exploiting spin symmetries to bypass the issue. However, in the presence of relativistic effects, the notion of spin and the associated symmetries become irrelevant. The key idea of BRUNCH is to develop a theoretical framework based on symmetries specifically adapted to the relativistic context: time-reversal and symmetries associated with the total angular momentum. This will enable the implementation of a methodological toolbox in relativistic quantum chemistry. It includes novel DFT methodologies able to accurately/quantitatively assess magnetic interactions and luminescence properties. BRUNCH will allow addressing critical issues at the heart of molecular magnetism, e.g. decoherence phenomena or the magneto-electric effect. By doing so, BRUNCH aims to revolutionise relativistic quantum chemistry and drive a major breakthrough in the field of molecular magnetism.