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SUMMARY:Symmetry in Multiple Hartree–Fock Self-Consistent-Field Solution
 s of Transition-Metal Complexes - Bang Huynh\, University of Cambridge
DTSTART:20181010T131500Z
DTEND:20181010T133500Z
UID:TALK109639@talks.cam.ac.uk
CONTACT:Lisa Masters
DESCRIPTION:The multiple Unrestricted Hartree–Fock (UHF) self-consistent
 -field (SCF) solutions of a model octahedral transition-metal complex\, [V
 F_6]^{3−} \, having V—F bond length of 1.9896 Å are located by metady
 namics in a 6-31G* basis and examined in terms of energy distribution and 
 symmetry properties. The use of Non-Orthogonal Configuration Interaction (
 NOCI) in conjunction with a careful analysis based on group and representa
 tion theories successfully restores spin and spatial symmetries of symmetr
 y-broken UHF solutions and gives multi-determinantal states that can be de
 finitively assigned to the expected electronic terms. The energy gaps betw
 een the best NOCI states for various electronic terms are consistent with\
 , and hence suggest\, a ligand-field splitting parameter ∆_o ≈ 13 130 
 cm^{−1} for this geometry when compared to the relevant Tanabe–Sugano 
 diagram. This thus sheds some light on the nature and ability of symmetry-
 broken UHF SCF solutions to incorporate static correlation. The analysis i
 s then extended to include a more general treatment of spin symmetry in th
 e framework of Complex Generalised Hartree–Fock (cGHF). However\, as thi
 s formulation is still in its infancy\, the results obtained are only prel
 iminary but nevertheless open up avenues for future investigations of gene
 ral spin and spatial symmetry breaking.
LOCATION:Department of Chemistry\, Cambridge\, Unilever lecture theatre
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