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SUMMARY:Holomorphic Hartree-Fock Theory: Exploiting Multiple SCF Solutions
  for Non-Orthogonal Configuration Interaction - Hugh Burton
DTSTART:20171011T134000Z
DTEND:20171011T140000Z
UID:TALK84071@talks.cam.ac.uk
CONTACT:Lisa Masters
DESCRIPTION:Although it is the lowest energy Hartree-Fock state that is us
 ually most sought after\, the non-linear self-consistent field (SCF) equat
 ions also admit a number of higher energy solutions that have been shown t
 o resemble excited molecular states. Motivated by this\, these states can 
 be used as a basis set for Non-Orthogonal Configuration Interaction (NOCI)
  to obtain adiabatic states which show similar properties to the results o
 f more expensive correlation techniques. However\, the existence of an SCF
  state across all molecular geometries is not guaranteed and there are man
 y known examples of coalescing solutions. The disappearance of a Hartree-F
 ock state severely hinders NOCI by leading to a sudden change in the basis
  set size\, resulting in discontinuous energy curves. In holomorphic Hartr
 ee-Fock theory\, a holomorphic analogue of the Hartree-Fock equations is c
 onstructed by removing the complex conjugation of orbital coefficients fro
 m the energy functional. By making this alteration\, SCF states that usual
 ly disappear as the molecular geometry is changed are instead found to ext
 end into the complex plane\, allowing a continuous basis to be constructed
  for NOCI. In this talk\, I present the theoretical and mathematical found
 ations of holomorphic Hartree-Fock theory and demonstrate its contribution
  to NOCI calculations.
LOCATION:Department of Chemistry\, Cambridge\, Unilever lecture theatre
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