BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:MD Simulations with Chemical Accuracy – Alkane Reactivity in Aci
 dic Zeolites - Dr Fabian Berger\, University of Cambridge
DTSTART:20231030T143000Z
DTEND:20231030T150000Z
UID:TALK207727@talks.cam.ac.uk
CONTACT:Dr Philipp Pracht
DESCRIPTION:The reduction of the carbon footprint is not possible without 
 innovations in heterogeneous catalysis. Before a molecule can undergo conv
 ersion\, it has to bind to a surface\, hence\, atomic understanding of ads
 orption on flat surfaces or in nano-sized pores is required for the ration
 al design of new catalytic processes and materials. \nAdsorption strongly 
 affects the reaction kinetics and diffusion within catalysts\, but inheren
 tly poses a multiscale problem. While thermal ensembles of adsorbates at f
 inite temperatures can only be properly described by approaches that sampl
 e the potential energy surface (PES) exhaustively\, e.g. molecular dynamic
 s (MD) simulations\, a chemically accurate description of adsorbate-host i
 nteractions requires post-Hartree Fock methods. The standard approach to c
 alculate adsorption enthalpies considers only the energetically most stabl
 e structure (“local” approach) on the PES and is based on density func
 tional theory augmented with dispersion terms (DFT-D). This approach is us
 ed almost exclusively\, despite its well-known shortcomings and large devi
 ations from the experiments – in our case about 17 kJ mol−1.\nWe int
 roduce a combined hybrid MP2:PBE+D2 MD approach that overcomes the proble
 ms. While the sampling of the configurational space is performed with MD a
 t the PBE+D2 level\, the enthalpies are based on MP2-quality energy surfac
 es. We use the MP2:PBE+D2 method to calculate MP2 corrections to adsorptio
 n enthalpies for selected snapshots and parameterize the difference betwee
 n PBE+D2 and MP2 based on a physically motivated two-dimensional linear mo
 del. This approach reduces the computation time for a “MP2-quality” MD
  of 100\,000 steps from about 340 years to 3 weeks.\nThe new methodology y
 ields chemically accurate adsorption enthalpies\, deviating only by 1.9 k
 J mol−1 for different alkanes (methane to n‑hexane) in various Brøns
 ted acidic zeolites (H‑MFI\, H‑CHA\, and H‑FAU) including low and hi
 gh Si/Al ratios ranging from 2.6 to 47. Insights from MD simulations in co
 mbination with accurate adsorption enthalpies are used to understand the b
 ehavior of adsorbates at experimental temperatures. Furthermore\, the new 
 method enables us to reach chemical accuracy for intrinsic enthalpy barrie
 rs as well. This is demonstrated for the monomolecular cracking reaction o
 f linear alkanes\, with rate constants improved by a factor of 50 compared
  to the "standard model" of computational catalysis.
LOCATION:Yusuf Hamied Department of Chemistry\, Pfizer Lecture Theatre\; Z
 oom link: https://zoom.us/j/92447982065?pwd=RkhaYkM5VTZPZ3pYSHptUXlRSkppQT
 09
END:VEVENT
END:VCALENDAR