Publications by authors named "Matthias Kick"
An accurate treatment of electronic spectra in large systems with a technique such as time-dependent density functional theory is computationally challenging. Due to the Nyquist sampling theorem, direct real-time simulations must be prohibitively long to achieve suitably sharp resolution in frequency space. Super-resolution techniques such as compressed sensing and MUSIC assume only a small number of excitations contribute to the spectrum, which fails in large molecular systems where the number of excitations is typically very large.
View Article and Find Full Text PDFArticle Synopsis
- The high density of trap states in III-V colloidal quantum dots (QDs) limits their use as nontoxic and tunable emitters.
- Using density functional theory (DFT), the study investigates trap state formation in passivated InP and GaP QDs, revealing that three-coordinate species primarily cause trapping.
- The research highlights differences in surface reconstruction between InP and GaP and proposes ways to control trap states based on this understanding.
Imposing quantum confinement has the potential to significantly modulate both the structural and optical parameters of interest in many material systems. In this work, we investigate strongly confined ultrathin perovskite nanoplatelets APbBr. We compare the all-inorganic and hybrid compositions with the A-sites cesium and formamidinium, respectively.
View Article and Find Full Text PDFArticle Synopsis
- The study addresses challenges in understanding the morphology of lead halide perovskite nanocrystals (LHP-NCs) due to limited synthetic strategies and ligands.
- It presents a novel synthesis method using zwitterionic ligands that enables the controlled production of LHP-NCs with different shapes, such as nanoplatelets and nanorods.
- By combining experimental results with theoretical calculations, the research identifies key factors influencing ligand binding on LHP-NC surfaces, which can inform future studies on these materials.
Quantum confined lead halide perovskite nanoplatelets are anisotropic materials displaying strongly bound excitons with spectrally pure photoluminescence. We report the controlled assembly of CsPbBr nanoplatelets through varying the evaporation rate of the dispersion solvent. We confirm the assembly of superlattices in the face-down and edge-up configurations by electron microscopy, as well as X-ray scattering and diffraction.
View Article and Find Full Text PDFZero strain insertion, high cycling stability, and a stable charge/discharge plateau are promising properties rendering Lithium Titanium Oxide (LTO) a possible candidate for an anode material in solid state Li ion batteries. However, the use of pristine LTO in batteries is rather limited due to its electronically insulating nature. In contrast, reduced LTO shows an electronic conductivity several orders of magnitude higher.
View Article and Find Full Text PDFArticle Synopsis
- Lithium titanium oxide (LiTiO) is a promising anode material for long-life batteries due to its phase stability during charging and discharging cycles.
- The main limitation of LiTiO is its low intrinsic electronic conductivity, which can potentially be improved by introducing oxygen vacancies to modify charge carrier transport.
- Using Hubbard corrected density functional theory, researchers find that polaronic states and their hopping mechanisms significantly contribute to the increase in electronic conductivity, informing on the charge mobility and stability of different localization patterns.
Intricacies of DFT+U, Not Only in a Numeric Atom Centered Orbital Framework.
J Chem Theory Comput
March 2019
We implemented the popular Hubbard density-functional theory + U (DFT+U) method in its spherically averaged form in the all-electron, full-potential DFT code FHI-aims. There, electronic states are expressed on a basis of highly localized numeric atomic orbitals (NAO), which straightforwardly lend themselves as projector functions for the DFT+U correction, yielding the necessary occupations of the correlated Hubbard subspace at no additional cost. We establish the efficacy of our implementation on the prototypical bulk NiO and obtain the well-known band gap opening effect of DFT+U.
View Article and Find Full Text PDF