Benchmark calculations with correlated molecular wavefunctions. XIII. Potential energy curves for He-2, Ne-2 and Ar-2 using correlation consistent basis sets through augmented sextuple zeta
T. Van Mourik et al., Benchmark calculations with correlated molecular wavefunctions. XIII. Potential energy curves for He-2, Ne-2 and Ar-2 using correlation consistent basis sets through augmented sextuple zeta, MOLEC PHYS, 96(4), 1999, pp. 529-547
The potential energy curves of the rare gas dimers He-2, Ne-2, and Ar-2 hav
e been computed using correlation consistent basis sets ranging from singly
augmented aug-cc-pVDZ sets through triply augmented t-aug-cc-pV6Z sets, wi
th the augmented sextuple basis sets being reported herein. Several methods
for including electron correlation were investigated, namely Moller-Plesse
t perturbation theory (MP2, MP3 and MP4) and coupled cluster theory [CCSD a
nd CCSD(T)]. For He-2 CCSD(T)/d-aug-cc-pV6Z calculations yield a well depth
of 7.35 cm(-1) (10.58 K), with an estimated complete basis set (CBS) limit
of 7.40 cm(-1) (10.65 K). The latter is smaller than the 'exact' well dept
h (Aziz, R. A., Janzen, A. R., and Moldover, M. R., 1995, Phys. Rev. Lett.,
74, 1586) by about 0.2 cm(-1) (0.35 K). The Net well depth, computed with
the CCSD(T)/d-aug-cc-pV6Z method, is 28.31 cm(-1) and the estimated CBS lim
it is 28.4 cm(-1) approximately 1 cm(-1) smaller than the empirical potenti
al of Aziz, R. A., and Slaman, M., J., 1989, Chem. Phys., 130, 187. Inclusi
on of core and core-valence correlation effects has a negligible effect on
the Nea well depth, decreasing it by only 0.04 cm(-1). For Ar-2, CCSD(T)/ d
-aug-cc-pV6Z calculations yield a well depth of 96.2 cm(-1). The correspond
ing HFDID potential of Aziz, R. A., 1993, J. chem. Phys., 99, 4518 predicts
of D-e of 99.7 cm(-1). Inclusion of core and core-valence effects in Ar-2
increases the well depth and decreases the discrepancy by approximately 1 c
m(-1).