# Alexandre Tkatchenko #### calendar\_today Date and Time **September 16, 2013** 02:00PM - 03:00PM EDT #### pin\_drop Location **Pfizer Lecture Hall** Joint Quantum Sciences Seminar (in Chemistry) Dr. Alexandre Tkatchenko, Fritz-Haber Institute "Collective van der Waals Interactions in Molecules and Solids" Joint Quantum Sciences Seminar Van der Waals (vdW) interactions are ubiquitous in molecules and condensed matter. These interactions are inherently quantum mechanical phenomena that arise from concerted electronic fluctuations within a given molecular system. Despite this fact, the vast majority of theoretical calculations include long-range vdW interactions based on a simple effective interatomic pairwise model. We introduce an efficient method that accurately describes the long-range many-body vdW energy and demonstrate that collective many-body contributions can significantly exceed the highly coveted "chemical accuracy". Cases studied include intermolecular binding energies, the conformational hierarchy of DNA structures, the geometry and stability of molecular crystals, including thermodynamic stability among competing molecular crystal polymorphs. Our findings suggest that inclusion of the many-body vdW energy is essential for achieving qualitatively correct behavior and therefore must be accounted for in molecular and solid-state simulations. Share on:- [ Facebook ](#) - [ Twitter ](#) - [ Linkedin ](#) Save: [ Add to calendar calendar\_today ](https://www.chemistry.harvard.edu/node/83386/event-feed.ics) Copy link link