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Friday, October 05

Role of van der Waals Interactions in
Physics, Chemistry, and Biology

Matthias Scheffler, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany
CNMS Discovery Seminar Series
11:00 AM — 12:00 PM, SNS Central Laboratory and Office Building (8600),
Iran Thomas Auditorium (Room A-103)
Contact: Sean Smith ( smithsc@ornl.gov), 865.574.5081

Abstract

Dispersive or van der Waals (vdW) interactions are crucial for the formation, stability, and function of many molecules and materials. They typically dominate in regions where the overlap of electron densities is small, i.e., at medium to long interatomic distances. Interestingly, the commonly applied implementations of density-function theory (like LDA, GGAs, hybrids) are completely lacking this vdW tail. And also at short interatomic distances, these approaches do not provide the correct physical/chemical description in systems were nonlocal correlation is playing a noticeable role. In this talk I will review recent advances in electronic-structure theory; in particular, I will highlight the exceptionally accurate and truly parameter-free "exact exchange (EX) plus random phase approximation to correlation (cRPA)" approach and recent corrections to cRPA. Furthermore, I will discuss approximations that are computationally more efficient and enable the treatment of large systems or long time-scale molecular dynamics. The main part of the talk deals with representative applications, e.g.,
  • The noticeable role of vdW interactions in the cohesion of noble metals and semiconductors and in the intermolecular interactions in water and ice.
  • Particular focus will be put on inorganic/organic interfaces, i.e., the adsorption of organic molecules at metals and at semiconductors, and on tuning the workfunction of the inorganic substrate by molecular acceptors.
  • Regarding biophysics, I will show that and how the inclusion of vdW interactions changes the conformational landscape, stabilizes the helical hydrogen bond network compared to plain DFT-GGA calculations, and thus enhances the thermal stability of helical structures by several hundred K.