A spin-adapted coupled-cluster based linear response theory for double ionization potentials

✍ Scribed by R. Chaudhuri; B. Datta; K. Das; D. Mukherjee

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 953 KB
• Volume: 60
• Category: Article
• ISSN: 0020-7608
• DOI: 10.1002/(sici)1097-461x(1996)60:1<347::aid-qua34>3.0.co;2-8

✦ Synopsis

We developed in this article a spin-adapted formiilation of the coupled-cluster based linear response theory (CC-LRT) for computing double-ionization potentials (DIPs), which may be experimentally observed by Auger spectroscopy. CC-LRT is a multireference generalization of the CC theory where the energy differences have no disconnected vacuum (core) diagrams, signifying core-extensivity. For the spin-adaptation of the CC-LRT equations for the singlet and triplet manifolds, we used the Young-Yamanouchi orthogonal spin-eigenfunctioris. The orbital version of the CC-LRT equations are then automatically generated by the conjugate projection operators of Young-Yamanouchi spin functions. We illustrated the working of our spin-adaptation procedure by confining our CC-LRT equations to the space of 2h and lp-3k ionized determinants. As numerical application of our formalism, we computed the Auger kinetic energies of HF and H,O. We also analyzed the nature of size-extensivity of the DIPs generated by CC-LRT and showed explicitly that when the molecule is composed of two noninteracting fragments the computed DIPs are either DIPs of fragment A or B or a composite DIP depending on both A and B, which are just not sum of ionization potentials (IPS) of A and B. This analysis is done to underscore the fact that DIPs from CC-LRT is only core-extensive and not fully extensive.