Nonempirical calculations on diatomic transition metals. II. RHF investigation of lowest closed‐shell states of homonuclear 3d transition‐metal dimers

Abstract

AbstractsPotential-energy curves of the 3d dimer series Sc2 through Cu2 are calculated for the lowest closed-shell states within the nonempirical RHF formalism using limited basis sets of minimal to near-double-zeta-plus-polarization size. Calculated spectroscopic constants are compared to semiempirical results as well as to experimental estimates. The possibility for closedor open-shell ground states is discussed for each dimer. For diatomic Sc and Cu a detailed study of basis set effects on calculated molecular constants is carried out.Des courbes de potentiel pour la serie des dimeres 3d de Sc, a Cuz ont etC calculkes pour les ttats i couches completes les plus bas par le proctdC RHF non-empirique avec des jeux de base limitts allant de bases minimales A des bases de type "presque double zCta et polarisation". Les constantes spectroscopiques calculkes sont comparees i des rtsultats semi-empiriques et a des estimations expirimentales. La nature de I'ttat fondamental-couche ouverte ou fermee-est discutee skparernent pour chaque dimere. Pour Sc et Cu diatomique une ttude detaillee des effects de la qualite de la base sur les constantes moltculaires a C t t faite.Potentialkurven der niedrigsten Zustande mit abgeschlossenen Schalen werden fur die 3d Dimerenserie von Scz bis Cuz in Rahmen des RHF-Formahnus berechnet. Die Basissatze sind von minimaler bis zur fast-Doppelzeta-plus-Polarisations-Grofle. Berechnete spektroskopische Konstanten werden mit halbempirischen und experimentellen Abschatzungen verglichen. Die Moglichkeit, ob der Grundzustand eine geschlossene oder offene Schale hat, wird einzeln fur jedes Dimer diskutiert. Fur diatomares Sc und Cu wird eine eingehende Untersuchung der Basissatzeffekte auf die berechneten niolekularen Konstanten durchgefuhrt.

Ultrashort Mn–Mn Bonds in Organometallic Complexes

“…Note, for example, that obtaining the minimum caused by van der Waals interactions ,, at distances larger than 3 Å requires using hybrid functionals or even the CASSCF (complete active space self-consistent field) method, which reproduces the antiferromagnetic coupling and the bond length larger than 3 Å obtained in experiments. ,− The strong Mn–Mn bonding in the Mn 2 molecule at short distances can therefore be computed accurately enough using generalized gradient approximation (GGA) functionals. The low-spin solutions (with 0 and 2 μ B ) shrink to local minima at bond lengths of about 1.8 Å, as reported previously. , The minimum at short distances is also favored in the bonding in Mn 2 Bz 2 because the magnetic moment in the 3d Mn levels is decreased by the Bz molecules, so the Mn–Mn distances are dramatically reduced.…”

“…The strong Mn-Mn bonding in the Mn 2 molecule at short distances can therefore be computed accurately enough using generalized gradient approximation (GGA) functionals. The low spin solutions (with 0 and 2 µ B ) shrink to local minima at bond lengths of about 1.8 Å, as reported previously [69,70]. The minimum at short distances is also favored in the bonding in Mn 2 Bz 2 because the magnetic moment in the 3d Mn levels is decreased by the Bz molecules, so the Mn-Mn distances are dramatically reduced.…”

“…The low-spin solutions (with 0 and 2 μ B ) shrink to local minima at bond lengths of about 1.8 Å, as reported previously. 87,88 The minimum at short distances is also favored in the bonding in Mn 2 Bz 2 because the magnetic moment in the 3d Mn levels is decreased by the Bz molecules, so the Mn−Mn distances are dramatically reduced.…”

Structure and properties of cobalt clusters up to the tetramer: A density-functional study

“…There is also a scarcity of theoretical studies in the literature. The only cluster investigated until now is the dimer: Co 2 has been studied by extended Hückel, 17 restricted Hartree-Fock, 18 configuration-interaction, 19 and local spin density 20 methods.…”

The electronic structure of Ti2 and Ti2+

“…Recently, Himmel and Bihlmeier 14 employing UV-visible and resonance Raman spectra of Ti 2 in noble gas matrices, reported D e (D 0 ) = 27.2 (26.6) kcal/mol, considerably lower than the 35.5 ± 4.4 kcal/mol of Russon et al 12 Finally, Hübner et al 15 in a combined experimental (visible absorption spectroscopy)-theoretical work, gave experimental ω e , ω e x e , and T e values for the upper 1 3 u , 1 3 u , 2 3 u , and 2 3 u states of Ti 2 . The first non-empirical calculations on the 3d-M 2 (M = Sc-Cu) series at the Hartree-Fock level were done by Wolf and Schmidtke, 16 who reported r e (X 1 g + ) = 1.87 Å and ω e = 580 cm −1 for the Ti 2 dimer. A few years later, Walch and Bauschlicher performed multireference configuration interaction (MRCI) calculations on Ti 2 .…”