Gold Behaves as Hydrogen in the Intermolecular Self-Interaction of Metal Aurides MAu(4) (M=Ti, Zr, and Hf)

Abstract

We performed density functional calculations to examine the intermolecular self-interaction of metal tetraauride MAu4 (M=Ti, Zr, and Hf) clusters. We found that the metal auride clusters have strong dimeric interactions (2.8-3.1 eV) and are similar to the metal hydride analogues with respect to structure and bonding nature. Similarly to (MH4)(2), the (mu-Au)(3) C-s structures with three three-center two-electron (3c-2e) bonds were found to be the most stable. Natural orbital analysis showed that greater than 96% of the Au 6s orbital contributes to the 3c-2e bonds, and this predominant s orbital is responsible for the similarity between metal aurides and metal hydrides (>99% H 1s). The favorable orbital interaction between occupied Au 6s and unoccupied metal d orbitals leads to a stronger dimeric interaction for MAu4-MAu4 than the interaction for MH4-MH4. There is a strong relationship between the dimeric interaction energy and the chemical hardness of its monomer for (MAu4)(2) and (MH4)(2).