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Abstract: A previous study of diatomic molecules revealed that variational second-orderdensity matrix theory has serious problems in the dissociation limit when theN-representability is imposed at the level of the usual two-index P, Q, G oreven three-index T1, T2 conditions H. van Aggelen et al., Phys. Chem. Chem.Phys. 11, 5558 2009. Heteronuclear molecules tend to dissociate intofractionally charged atoms. In this paper we introduce a general class ofN-representability conditions, called subsystem constraints, and show that theycure the dissociation problem at little additional computational cost. As anumerical example the singlet potential energy surface of BeB+ is studied. Theextension to polyatomic molecules, where more subsystem choices can beidentified, is also discussed.



Author: Brecht Verstichel, Helen van Aggelen, Dimitri Van Neck, Paul W. Ayers, Patrick Bultinck

Source: https://arxiv.org/







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