Measuring Electron Correlation. The Impact of Symmetry and Orbital
Transformations
- URL: http://arxiv.org/abs/2301.12807v2
- Date: Thu, 6 Apr 2023 10:50:51 GMT
- Title: Measuring Electron Correlation. The Impact of Symmetry and Orbital
Transformations
- Authors: R\'obert Izs\'ak, Aleksei V Ivanov, Nick S. Blunt, Nicole Holzmann,
Frank Neese
- Abstract summary: Measures of electron correlation used in wavefunction theory, density functional theory and quantum information theory are briefly reviewed.
We focus on a more traditional metric based on dominant weights in the full configuration solution.
The impact of symmetry is discussed and we emphasize that the distinction between determinants, configuration state functions and configurations as reference functions is useful.
- Score: 0.0
- License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
- Abstract: In this perspective, the various measures of electron correlation used in
wavefunction theory, density functional theory and quantum information theory
are briefly reviewed. We then focus on a more traditional metric based on
dominant weights in the full configuration solution and discuss its behaviour
with respect to the choice of the $N$-electron and the one-electron basis. The
impact of symmetry is discussed and we emphasize that the distinction between
determinants, configuration state functions and configurations as reference
functions is useful because the latter incorporate spin-coupling into the
reference and should thus reduce the complexity of the wavefunction expansion.
The corresponding notions of single determinant, single spin-coupling and
single configuration wavefunctions are discussed and the effect of orbital
rotations on the multireference character is reviewed by analysing a simple
model system. In molecular systems, the extent of correlation effects should be
limited by finite system size and in most cases the appropriate choices of
one-electron and $N$-electron bases should be able to incorporate these into a
low-complexity reference function, often a single configurational one.
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