arXiv subjects

Heike Fliegl

Publications and source records attributed to Heike Fliegl.

3 recordsLinked to original sources

arXiv2025

Research Knowledge Graphs in NFDI4DataScience: Key Activities, Achievements, and Future Directions

As research in Artificial Intelligence and Data Science continues to grow in volume and complexity, it becomes increasingly difficult to ensure transparency, reproducibility, and discoverability. To address these challenges, as research artifacts should be understandable and usable by machines, the NFDI4DataScience consortium is developing and providing Research Knowledge Graphs (RKGs). Building upon earlier works, this paper presents recent progress in creating semantically rich RKGs using standardized ontologies, shared vocabularies, and automated Information Extraction techniques. Key achievements include the development of the NFDI4DS ontology, metadata standards, tools, and services designed to support the FAIR principles, as well as community-led projects and various implementations of RKGs. Together, these efforts aim to capture and connect the complex relationships between datasets, models, software, and scientific publications.

cs.IR↗

arXiv2021

Spatial contributions to nuclear magnetic shieldings

We develop a methodology for calculating, analyzing and visualizing nuclear magnetic shielding densities, which are calculated from the current density via the Biot-Savart relation. Atomic contributions to nuclear magnetic shielding constants can be estimated within our framework with a Becke partitioning scheme. The new features have been implemented in the GIMIC program and are applied in this work to the study of the $^1$H and $^{13}$C nuclear magnetic shieldings in benzene (C$_6$H$_6$) and cyclobutadiene (C$_4$H$_4$). The new methodology allows a visual inspection of the spatial origins of the positive (shielding) and negative (deshielding) contributions to the nuclear magnetic shielding constant of a single nucleus, something which has not been hitherto easily accomplished. Analysis of the shielding densities shows that diatropic and paratropic current-density fluxes yield both shielding as well as deshielding contributions, as the shielding or deshielding is determined by the direction of the current-density flux with respect to the studied nucleus instead of the tropicity. Becke partitioning of the magnetic shieldings shows that the magnetic shielding contributions mainly originate from the studied atom and its nearest neighbors, confirming the localized character of nuclear magnetic shieldings.

physics.chem-ph↗

arXiv2021

Benchmarking magnetizabilities with recent density functionals

We have assessed the accuracy for magnetic properties of a set of 51 density functional approximations, including both recently published as well as already established functionals. The accuracy assessment considers a series of 27 small molecules and is based on comparing the predicted magnetizabilities to literature reference values calculated using coupled cluster theory with full singles and doubles and perturbative triples [CCSD(T)] employing large basis sets. The most accurate magnetizabilities, defined as the smallest mean absolute error, were obtained with the BHandHLYP functional. Three of the six studied Berkeley functionals and the three range-separated Florida functionals also yield accurate magnetizabilities. Also some older functionals like CAM-B3LYP, KT1, BHLYP (BHandH), B3LYP and PBE0 perform rather well. In contrast, unsatisfactory performance was generally obtained with Minnesota functionals, which are therefore not recommended for calculations of magnetically induced current density susceptibilities, and related magnetic properties such as magnetizabilities and nuclear magnetic shieldings. We also demonstrate that magnetizabilities can be calculated by numerical integration of the magnetizability density; we have implemented this approach as a new feature in the gauge-including magnetically induced current method (GIMIC). Magnetizabilities can be calculated from magnetically induced current density susceptibilities within this approach even when analytical approaches for magnetizabilities as the second derivative of the energy have not been implemented. The magnetizability density can also be visualized, providing additional information that is not otherwise easily accessible on the spatial origin of the magnetizabilities.

physics.chem-ph↗