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SUMMARY:Quantum Monte Carlo Modeling of π-bonded Transition-metal Organom
 etallics - Prof Ivan Stich\,Institute of Physics\, Slovak Academy of Scien
 ces\, Slovakia
DTSTART:20121129T141500Z
DTEND:20121129T151500Z
UID:TALK40982@talks.cam.ac.uk
CONTACT:Dr G Moller
DESCRIPTION:The talk will focus on complexes of 3d transition metal atoms 
 ( TM ) with benzene molecule(s). These systems represent one of the most i
 mportant families of π-bonded organometallics. Among the most important a
 nd intriguing applications is the use of sandwich-type TM-benzenes as spin
  valves\, featuring system-size dependent metallic behavior for the majori
 ty spin electrons and a semiconductor gap for the minority spin electrons 
 [1].\nWe will present accurate quantum Monte Carlo (QMC) calculations [2] 
 which enabled us to determine the structure\, spin multiplicity\, ionizati
 on energy\, dissociation energy\, and spin-dependent electronic gaps of th
 e short-sandwich vanadium- and cobalt-benzene systems and their cations. F
 or this purpose we have used a multi-stage combination of techniques with 
 consecutive elimination of all systematic biases except for the fixed-node
  approximation in QMC. Our calculations illustrate the scatter and signifi
 cant differences in DFT spin multiplicities and dissociation energies whic
 h sensitively depend on the used exchange-correlation functional. Hence\, 
 our results significantly differ from the established picture based on les
 s accurate calculations (gradient corrected\, hybrid\, meta hybrid\, and d
 ouble hybrid DFT). The results enabled us to reveal the DFT biases which a
 re of the order of ≈0.5 eV. At the same time our study exposes the short
 comings and biases of the existing experimental results and point out the 
 importance of high-level many-body methods for predictive calculations of 
 similar TM-based organometallic systems. \n\n# V. V. Maslyuk et al.\, Phys
 . Rev. Lett. 97\, 097201 (2006).                                          
       \n# L. Horváthová\, M. Dubecký\, L. Mitas\, and I. Štich\, Phys.
  Rev. Lett. 109\, 053001 (2012).
LOCATION:TCM Seminar Room\, Cavendish Laboratory
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