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MO: Molekülphysik

MO 7: Posters Wednesday: Theory: Structure and Dynamics

MO 7.9: Poster

Mittwoch, 4. April 2001, 12:30–15:00, AT3

Ab initio CALCULATIONS ON MOLECULAR STRUCTURE OF Mg₂ — •E. Czuchaj and M. Krośnicki — Institute of Theoretical Physics and Astrophysics, University of Gdańsk, Wita Stwosza 57, 80-952 Gdańsk, Poland

Adiabatic potential energies for the ground state and several low-lying excited states of the Mg₂ dimer have been calculated using the ab initio complete-active-space multiconfiguration self-consistent-field (CASSCF)/ complete-active-space multireference second-order perturbation theory (CASPT2) calculations. The calculations were performed by means of MOLPRO program using the contracted (20s14p4d3f2g)/[14s12p4d3f2g] cc-p V5Z orbitals of Dunning for Mg augmented with two diffuse s and p atomic orbitals. In the calculations, 24 electrons of the species were correlated to obtain the X¹Σ_g⁺, ³Π_g, ³Σ_u, ³Π_u, ³Σ_g, ¹Π_g, ¹Σ_u, (1)¹Π_u, (2)¹Π_u and (2)¹Σ_g potential curves in the internuclear separation range from 3.0 to 40.0 a₀. The obtained potential curves are qualitatively similar to the ones calculated earlier by Stevens and Krauss, but some quantitative differences occur. Comparison between the present potential curves and experimentally known X¹Σ_g⁺ and ¹Σ_u⁺ energy curves shows very good agreement for both the bond strength D_e and bond length R_e. In general, the present potential curves are considerably deeper than that calculated by Stevens and Krauss, particularly it concerns the (1)¹Π_u potential curve. In addition, using the Breit-Pauli operator, the spin-orbit coupling between the ¹Σ_u and ³Π_u states as well as between the ¹Π_g and two triplet ³Σ_g and ³Π_g states have been computed as a function of internuclear separation.