The seniority quantum number in Tensor Network States
Klaas Gunst, Dimitri Van Neck, Peter Andreas Limacher, Stijn De Baerdemacker
Abstract
We employ tensor network methods for the study of the seniority quantum number – defined as the number of unpaired electrons in a many-body wave function – in molecular systems. Seniority-zero methods recently emerged as promising candidates to treat strong static correlations in molecular systems, but are prone to deficiencies related to dynamical correlation and dispersion. We systematically resolve these deficiencies by increasing the allowed seniority number using tensor network methods. In particular, we investigate the number of unpaired electrons needed to correctly describe the binding of the neon and nitrogen dimer and the \mathbf{D_{6h}} <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mstyle mathvariant="bold"> <mml:msub> <mml:mi>D</mml:mi> <mml:mrow> <mml:mn>6</mml:mn> <mml:mi>h</mml:mi> </mml:mrow> </mml:msub> </mml:mstyle> </mml:math> symmetry of benzene.