Pyrite (FeS2), being a promising material for future solar technologies, has so far exhibited in experiments an open-circuit voltage (OCV) of around 0.2 V, which is much lower than the frequently quoted ‘accepted’ value for the fundamental bandgap of ∼0.95 eV. Absorption experiments show large subgap absorption, commonly attributed to defects or structural disorder. However, computations using density functional theory with a semi-local functional predict that the bottom of the conduction band consists of a very low intensity sulfur p-band that may be easily overlooked in experiments because of the high intensity onset that appears 0.5 eV higher in energy. The intensity of absorption into the sulfur p-band is found to be of the same magnitude as contributions from defects and disorder. Our findings suggest the need to re-examine the value of the fundamental bandgap of pyrite presently in use in the literature. If the contribution from the p-band has so far been overlooked, the substantially lowered bandgap would partly explain the discrepancy with the OCV. Furthermore, we show that more states appear on the surface within the low energy sulfur p-band, which suggests a mechanism of thermalization into those states that would further prevent extracting electrons at higher energy levels through the surface. Finally, we speculate on whether misidentified states at the conduction band onset may be present in other materials.

The ease by which graphene is affected through contact with other materials is one of its unique features and defines an integral part of its potential for applications. Here, it will be demonstrated that intercalation, the insertion of atomic layers in between the backside of graphene and the supporting substrate, is an efficient tool to change its interaction with the environment on the frontside. By partial intercalation of graphene on Ir(111) with Eu or Cs we induce strongly n-doped graphene patches through the contact with these intercalants. They coexist with nonintercalated, slightly p-doped graphene patches. We employ these backside doping patterns to directly visualize doping induced binding energy differences of ionic adsorbates to graphene through low-temperature scanning tunneling microscopy. Density functional theory confirms these binding energy differences and shows that they are related to the graphene doping level.

The zigzag edges of graphene on Ir(111) are studied by ab initio simulations and low-temperature scanning tunneling spectroscopy, providing information about their structural, electronic, and magnetic properties. No edge state is found to exist, which is explained in terms of the interplay between a strong geometrical relaxation at the edge and a hybridization of the d orbitals of Ir atoms with the graphene orbitals at the edge.

In this highlight we briefly review several of our recent theoretical studies focused on how the interplay between the chemical and the van der Waals interactions determines the bonding mechanism of several chemically functionalized π-conjugated organic molecules on non-magnetic and magnetic surfaces. In particular, we focus on the issue how to tailor the strength of the interaction between such π-conjugated organic molecules with a substrate of choice such that the nature of the molecular bonding has the specific features of the physisorption or chemisorption processes. Furthermore, we show how the precise control of these binding mechanisms allows us to design specific electronic and magnetic properties of hybrid organic-metallic interfaces.

In this paper, we present a first principles high throughput screening system to search for new water-splitting photocatalysts. We use the approach to screen through nitrides and oxynitrides. Most of the known photocatalytic materials in the screened chemical space are reproduced. In addition, sixteen new materials are suggested by the screening approach as promising photocatalysts, including three binary nitrides, two ternary oxynitrides and eleven quaternary oxynitrides.

Explorations of the ore bodies Prlovi 1, Prlovi 2 and Z of the mined ore deposit Prlovi have included ore microscopy of mineral samples from many boreholes. The orebody Prlovi 2 is prospective for the lead (4%) and zinc (3%) concentrations of which 1.89% Pb and 1.58% Zn occur in sulphides and 2.17% and 1.44% in oxides. The purpose of the ore microscopy was to recommend, based on mineral composition and texture, how to enrich the complex sulphideoxide mineral. The paper describes the composition of the intergrown minerals and suggests the method of the mineral product recovery. Illustrations in the paper are good representative microphotographs of the identified and characteristic structural features.

Density functional theory (DFT) has been steadily improving over the past few decades, becoming the standard tool for electronic structure calculations. The early local functionals (LDA) were eventually replaced by more accurate semilocal functionals (GGA) which are in use today. A major persisting drawback is the lack of the nonlocal correlation which is at the core of dispersive (van der Waals) forces, so that a large and important class of systems remains outside the scope of DFT. The vdW-DF correlation functional of Langreth and Lundqvist, published in 2004, was the first nonlocal functional which could be easily implemented. Beyond expectations, the nonlocal functional has brought significant improvement to systems that were believed not to be sensitive to nonlocal correlations. In this paper, we use the example of graphene nanodomes growing on the Ir(111) surface, where with an increase of the size of the graphene islands the character of the bonding changes from strong chemisorption towards almost pure physisorption. We demonstrate how the seamless character of the vdW-DF functionals makes it possible to treat all regimes self-consistently, proving to be a systematic and consistent improvement of DFT regardless of the nature of bonding. We also discuss the typical surface science example of CO adsorption on (111) surfaces of metals, which shows that the nonlocal correlation may also be crucial for strongly chemisorbed systems. We briefly discuss open questions, in particular the choice of the most appropriate exchange part of the functional. As the vdW-DF begins to appear implemented self-consistently in a number of popular DFT codes, with numerical costs close to the GGA calculations, we draw the attention of the DFT community to the advantages and benefits of the adoption of this new class of functionals.

We have performed a systematic semi-empirical and ab initio van der Waals study to investigate the bonding mechanism of benzene (C6H6), triazine (C3N3H3) and borazine (B3N3H6) adsorbed on graphene and a single boron nitride (BN) sheet. The two semi-empirical approaches used to include the van der Waals (vdW) interactions in our density functional theory (DFT) calculations suggest that the strength of the molecule–surface interaction corresponds to a strong physisorption with no net charge transfer between the molecules and the corresponding substrates. This observation is strengthened by the use of first-principles non-local correlation vdW-DF functionals which provide a sound physical basis to include vdW interactions in DFT calculations. In particular we have employed two flavors of vdW-DF functionals which enabled us to determine the role of the non-local correlation effects in the molecule–surface bonding mechanism which cannot be assessed by using only semi-empirical vdW methods. Our study also reveals that the strength of the molecule–surface interaction can be influenced by the electronegativity of the B, C and N atoms.