Periodic Reporting for period 1 - ReReDMFT (Development and implementation of reduced density matrix functionals for relativistic quantum chemistry.)
Reporting period: 2021-02-01 to 2023-01-31
The aim of the Relativistic Reduced Density Matrix Functional Theory project (891647-ReReDMFT) was to propose a new methodology for studying (theoretically) compounds formed by heavy elements using quantum mechanics. The electronic structure of heavy elements is modified by relativistic effects as a consequence of the high speed (that approaches the speed of light) of the electrons; thus, relativistic quantum mechanics is the framework needed for studying these compounds. In principle, the exact method to account for relativistic and quantum effects is known. But, the computational cost of the exact method makes it impractical. Hence, numerical simulations to study the chemistry and physics of compounds formed by heavy elements require approximations. In this project, I proposed to extend the applicability of Reduced Density Matrix Functional Theory (RDMFT) to include relativistic effects (ReRDFMT). This new method should lead to an affordable computational cost and facilitate the study of compounds formed by heavy elements. The Chemistry of heavy elements plays a crucial role in several applications of modern societies, e.g.: a) medical treatments employ their radioactive properties, b) power plants involve nuclear fission, c) the development of new nanomaterials [e.g. molecular engines is based on Ln(II) and Ln(III) for the photoconversion], among others. Thence, with the new theory/method proposed in this project (i.e. ReRDMFT) we will be able, in the future, to improve several scientific disciplines and industrial applications, which will also have a deep impact in our societies. The main objective of this project was to propose the theoretical foundations of ReRDMFT and propose the approximations needed for numerical simulations. The second objective was to develop a computational program to be used in numerical simulations of compounds formed by heavy elements. Finally, I aimed to compute some systems of scientific and industrial interests to describe the quality of ReRDMFT and compare them with reference data. I would like to conclude this project by highlighting that thanks to the financial support of the Marie Skłodowska Curie Action, the major objective of this project is completed and a new theory/method has been proposed. Nevertheless, I would also like to comment that the remaining (secondary) objectives are not completed and it is work that is still in progress.
During the first year, I completed the first objective of this project and published the new theory (ReRDFMT) in an open-access scientific journal (see M. Rodríguez-Mayorga, et al., SciPost Chem. 1, 004 (2022) for more details). Moreover, this new theory (ReRDMFT) was presented to the scientific community at five international conferences. Then, the initial training period using the DIRAC program to run computational simulations to generate a database was replaced by a study of the relativistic effects on electronic pair densities using the DIRAC program. This study was also published in an open-access scientific journal (see M. Rodríguez-Mayorga, et al., J. Chem. Phys. 157, 194301 (2022) for more details). Also, this study was presented at two international conferences to the scientific community. This study unveiled new insights about relativistic effects in the matter, we observed that relativistic effects reduce the mean inter-electronic distance and bring the electrons closer together. In terms of computational software, I have also advanced in the construction of the computational software needed to run the numerical ReRDFMT simulations. This software is already available on a GitHub server (https://github.com/marm314/standalone_noft.git(opens in new window)) to compute systems within a non-relativistic framework (RDMFT); it has been incorporated in major software packages (e.g. in MOLGW program). But, this software is not terminated due to the high complexity of the relativistic problem; It will be completed in the future. Similarly, the numerical simulations of compounds formed by heavy elements and their comparison with reference data will be performed in the future (as soon as the software will be made available). At the end of this project, a presentation was given to high school students at the I.E.S. Chaves Nogales in Sevilla - Spain about the use of computers to do chemistry (i.e. computational Chemistry). This presentation was given to 60 students in their third year of high school. Unfortunately, the COVID-19 restrictions have reduced the possibility of disseminating this project to a more broaden audience in social meetings.
Within this project, a new theory and method to study compounds formed by heavy elements have been proposed. And, the applicability of RDFMT has been extended to include relativistic effects. Also, our understanding of relativistic effects on the electronic structure has improved thanks to our study of relativistic effects on electronic pair densities. On the other hand, the software developed that is already in use in major packages (e.g. MOLGW program) extends the applicability of RDMFT; it will be exploited to design novel materials (e.g. materials presenting the effects of the so-called entanglement that are important in quantum information and that will have a crucial impact in the future of communications, security, etc.). Also, let me remark that as soon as software will be terminated (i.e. including the missing relativistic effects) it will serve to accelerate the computation of systems formed by heavy elements that will have an immediate impact in several disciplines (e.g. biology, medicine, material science, etc) and, then, in the industry. Let me highlight that heavy-elements take up more than one-third of the periodic table, which makes them present in aspects of our daily life. Thanks to this grant, I have been able to open a new avenue for studying compounds where relativistic and quantum effects need to be accounted for and a reasonable computational cost.