We devise a mixing algorithm for full-potential (FP) all-electron calculations in the linearized augmented planewave (LAPW) method. Pulay’s direct inversion in the iterative subspace is complemented with the Kerker preconditioner and further improvements to achieve smooth convergence, avoiding charge sloshing and noise in the exchange–correlation potential. As the Kerker preconditioner was originally designed for the planewave basis, we have adapted it to the FP-LAPW method and implemented in the exciting code. Applications to the 2 × 2 Au(111) surface with a vacancy and to the Pd(111) surface demonstrate that this approach and our implementation work reliably with both density and potential mixing.
We
carry out first-principles calculations of the quasi-particle
band structure and optical absorption spectra of H-passivated armchair
MoS2 nanoribbons (AMoS2NRs) by employing the
approach combining the Green’s function perturbation theory
(GW) and the Bethe-Salpeter equation (BSE), i.e., GW+BSE. Optical absorption spectra of AMoS2NRs
show the exciton multibands (their binding energies are close to or
less than 1 eV) which are much stronger than a single layer of MoS2. However, they are absent in the spectra by the approach
of GW and the random phase approximation (RPA), i.e., GW+RPA. This signifies that the excitonic correlation effects
are strongly enhanced in the reduced dimensional structure of MoS2. We also calculate the exciton wave functions for the few
lowest energy excitons, which are found to have non-Frenkel character.
Electrode/electrolyte interfaces play a crucial role in many electrochemical energy conversion and storage technologies. Hence, a deep understanding of the interfacial structure, energetic alignment and processes is of high relevance and has triggered the development of a number of in situ and operando techniques. One approach for gaining information about the change in surface chemistry and structure on an atomic scale is reflection anisotropy spectroscopy (RAS). This review presents and discusses the continuing effort to develop RAS as an in situ optical probe for solid‐liquid interfaces under applied potentials. Experimental and computational basic principles are presented and key challenges of electrochemical RAS are highlighted. Furthermore, we exemplarily demonstrate the potential of the method for spectroelectrochemistry, focusing on indium phosphide‐ and gold‐aqueous electrolyte interfaces as exemplary case studies, and outline research directions for battery systems.
The possibility of modifying the work function of electrodes is important for optimizing the energy barriers for charge-injection (extraction) at the interface to an organic material. In this study, we perform density-functional-theory calculations to investigate the impact of dithiol-terminated polyethylene glycol (PEG(thiol)) based self-assembled monolayers (SAMs) with different numbers of PEG repeat units on the work function of the Au(111) surface. We find that a monolayer of PEG(thiol) decreases the work function of the Au(111) surface, where the magnitude of this reduction strongly depends on the length of the PEG backbone. The main contribution arises from the dipole due to the adsorption-induced charge rearrangement at the interface. Our work reveals a pronounced odd-even effect, which can be traced back to the dipole moment of the PEG(thiol) layer.
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