Stuart Shepard

University of Twente | UT · Faculty of Science and Technology (TNW)

We show that recently developed quantum Monte Carlo methods, which provide accurate vertical transition energies for single excitations, also successfully treat double excitations. We study the double excitations in medium-sized molecules, some of which are challenging for high-level coupled-cluster calculations to model accurately. Our fixed-node...

We show that recently developed quantum Monte Carlo methods, which provide accurate vertical transition energies for single excitations, also successfully treat double excitations. We study the double excitations in medium-sized molecules, some of which are challenging for high level coupled-cluster calculations to model accurately. Our fixed-node...

The rational design of single-molecule electrical components requires a deep and predictive understanding of structure-function relationships. Here, we explore the relationship between chemical substituents and the conductance of metal-single-molecule-metal junctions, using functionalized oligophenylenevinylenes as a model system. Using a combinati...

The rational design of single molecule electrical components requires a deep and predictive understanding of structure-function relationships. Here we explore the relationship between chemical substituents and the conductance of metal-single molecule-metal junctions, using functionalized oligophenylenevinylenes as a model system. Using a combinatio...

Integrating graphene into electronic devices requires support by a substrate and contact with metal electrodes. Ab initio calculations at the level of density functional theory are performed on graphene-fcc-metal(111) [Gr/M(111)] (M = Ni, Cu, Au) systems. The strongly constrained and appropriately normed (SCAN) and SCAN with the revised Vydrov-van...

The process of physisorption on graphene is of recent interest due to its vast applications, such as an atomic sensor, in electronics and energy storage. Density functional theory (DFT) was used to determine the adsorption energies and distances of X-graphene (X = He, Ne, Ar, Kr, Xe, Rn) systems. The accuracy of DFT relies heavily on the choice of...

Calculating accurate band gaps of semiconducting and insulating materials is one of the major challenges currently facing density functional theory (DFT) calculations. The atomic and electronic structure of antiferromagnetic NiWO4 and CuWO4 is studied in the plane wave based program VASP using pure, as well as hybrid forms of the exchange-correlati...