Accurately solving the electronic Schrodinger equation of atoms and molecules using explicitly correlated (r_(12)-)MR-CI. The ground state of beryllium dimer (Be_2)

摘要

The recently proposed (explicitly correlated) r_(12)-MR-ACPF method is applied to the ground state (X~1#SIGMA#_g~+) potential of Be_2. A large [19s11p6d4f3g2h] basis set and a valence-CAS reference space (60 CSFs) are used. At long range, the reference space is augmented by {3s, 3p} orbitals (568 CSFs). The calculated dissociation energy (898 +- 8 cm~(-1)) is considerably larger than the experimental estimate (790 +- 30 cm~(-1)). The other molecular constants, however, are in good agreement. Our potential is close to the one calculated by Starck and Meyer [Chem. Phys. Lett. 258 (1996) 421].