1 1 Molecular systems , growth and overlayers : van der Waals density functional and first-principle thermodynamics calculations

Figure 1: Molecular systems which are part of our computational laboratory for development and accuracy calibration of van der Waals density functional (vdWDF) calculations [1]. With SNIC resources we pursue projects to determine binding in graphitics test systems — from C60 dimers (a) to graphene exfoliation [2] — and in molecular crystals such as cubane (b) [3]. We furthermore use vdW-DF to characterize molecular physisorption and adsorbate diffusion barriers (c) [4]. Unlike most semi-empirical approaches (like DFT-D), the vdW-DF method 2 provides a natural framework for inclusion of image-plane effects [5], a prerequisite for achieving transferability across a range of distances [3, 5, 6]. It is gratifying that a detailed calibration against the measured shape of the physisorption well for H2 on Cu(111) (d) [7] suggests a strong performance particularly for the most recent formulation, vdW-DF2, and a possibility to refine descriptions of, for example, lateral adsorbate interactions [4] and DNA structure [8].