Multi-reference coupled-cluster study of the ionic-neutral curve crossing LiF

Abstract

The recently developed exponential multi-reference wavefunction ansatz [J. Chem. Phys. 123 (2005) 84102] and the single-reference formalism multi-reference coupled cluster ansatz [J. Chem. Phys. 94 (1991) 1229] are applied to calculate the potential energy surface of LiF. The avoided crossing region for the ionic and the covalent ¹Σ⁺ states are analysed using plain self-consistent field and state averaged complete active space orbitals. Additionally, dipole moments are reported. All results are discussed and compared with full and multi-reference configuration interaction calculations.

Keywords:

• coupled-cluster
• multi-reference
• state selective
• electronic structure
• MRCC
• LiF

Acknowledgements

The author would like to thank the Institute for Nuclear Theory at the University of Washington for its hospitality on the occasion of the ‘Atomic, chemical and nuclear developments in coupled cluster methods’ (INT 08-2A) program.

Support by the Deutsche Forschungsgemeinschaft (grant HA 5116/1-1 and SPP 1145) is gratefully acknowledged.