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SUMMARY:General embedded cluster protocol for accurate modelling of oxygen
  vacancies in metal-oxides - Benjamin Shi (University of Cambridge)
DTSTART:20220223T143000Z
DTEND:20220223T150000Z
UID:TALK169817@talks.cam.ac.uk
CONTACT:Lisa Masters
DESCRIPTION:The O vacancy (Ov) formation energy\, EOv\, is an important pr
 operty of a metal-oxide\, governing its performance in applications such a
 s fuel cells or heterogeneous catalysis. These defects are routinely studi
 ed with density functional theory (DFT). However\, it is well-recognized t
 hat standard DFT formulations (e.g.\\ the generalized gradient approximati
 on) are insufficient for modelling the Ov\, requiring higher levels of the
 ory. The embedded cluster method offers a promising approach to compute EO
 v accurately\, giving access to all electronic structure methods. Central 
 to this approach is the construction of quantum(-mechanically treated) clu
 sters placed within suitable embedding environments. Unfortunately\, curre
 nt approaches to constructing the quantum clusters either require large sy
 stem sizes\, preventing application of high-level methods\, or require sig
 nificant manual input\, preventing investigations of multiple systems simu
 ltaneously. In this work\, we present a systematic and general quantum clu
 ster design protocol that can determine small converged quantum clusters f
 or studying the Ov in metal-oxides with accurate methods such as local cou
 pled cluster with singles\, doubles plus perturbative triples excitations 
 [CCSD(T)]. We apply this protocol to study the Ov in the bulk and surface 
 planes of rutile TiO2 and rocksalt MgO\, producing the first accurate and 
 well-converged determinations of EOv with this method. These reference val
 ues are used to benchmark exchange-correlation functionals in DFT and we f
 ind that all studied functionals underestimate EOv\, with the average erro
 r decreasing along the rungs of Jacob's ladder. This protocol is automatab
 le for high-throughput calculations and can be generalized to study point 
 defects or adsorbates.
LOCATION:Wolfson Lecture Theatre\, Dept. of Chemistry &amp\; Zoom
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