ISSN:
0020-7608
Keywords:
Computational Chemistry and Molecular Modeling
;
Atomic, Molecular and Optical Physics
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Bonding in transition-metal molecules presents novel features: (i) s electron bonding is overcome by multiple d electron bonding, (ii) intraatomic exchange favoring atomic magnetization competes with bonding that tends to pair the electrons, and (iii) in the heteronuclear dimers, the ionic terms may be important due to strong charge-transfer effects. The NbIr heteronuclear diatomic molecule shows all these features clearly. The cellular multiple scattering-xαβ calculation presented in this paper shows the ground state to correspond to antiferromagnetic coupling between the highly magnetic Nb atom and the Ir atom. A one-electron charge transfer from Nb to Ir was found; the result is an ionic structure, Nb+Ir-, for the dimer. The computed equilibrium distance, 4.100 a.u., corresponds to a region where d bonding strongly overcomes the s bonding, which alone would have stabilized the molecule at 5.950 a.u. At intermediate interatomic separations, 5.35 a.u., the NbIr system has a state in which all molecular orbitals are bonding with a high hybridization between the ns and (n - 1)d electrons of each atom, resulting in a (almost entirely) covalent high multiple-bond formation for this meta-stable state of the dimer.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/qua.560390506
