The Electronic Structure of Alkali Aurides. A Four-Component Dirac−Kohn−Sham Study

Predicting the stability and electronic structure of alkali metal aurides

Density functional theory calculations of phonon modes predict that some compounds of the alkali metal aurides family, general formulaA₂MAu₆(A= K, Rb or Cs;M= Ti, Zr, Hf, Sn or Pb), have stable three-dimensional phase with a double perovskite-type structure and cubicFm3¯mspace group (K₂PtCl₆-type). Bader's charge analysis shows that most electron density is located within the six atoms at the octahedra vertices like double perovskite halides. However, the short spacing between Au anions enables d-orbital interactions between them. Compounds of this family, with group 4 metals only, carry conduction states around the Γ point (k= 0). On the other hand, compounds with group 14 metals possess more conduction states around all the Brillouin zone and have electron pockets in their band structures. These compounds provide further insights into the unusual anionic behavior of gold and present other alternatives for the construction of divergent nanodevices.

Dopant induced modulation in the structure and electronic properties of Au10 cluster

DFT calculations at PBE0/SDD ∪ 6-31++G(d,p) level suggest that doped Au₁₀ clusters (with alkali and alkaline earth metals as dopants) are better potential candidates for use in heterogeneous catalysis.

The uncertain bond energy of the NaAu molecule: experimental redetermination and coupled cluster calculations

The dissociation energy of the intermetallic molecule NaAu, for which two largely at variance experimental values are available in the literature, has been redetermined by the Knudsen effusion mass spectrometry method. The molecule has been produced in the vapor phase by a specially designed experimental setting inspired by the double oven technique. The equilibrium of dissociation to atoms as well as the exchange equilibrium with the gold dimer were monitored mass-spectrometrically over about a 600 K temperature range. The third-law analysis of the equilibrium data provides the dissociation energy D0° (NaAu, g) = 245.3 ± 6.8 kJ/mol, corresponding to a formation enthalpy at 298 K of 228.3 ± 7.5 kJ/mol. The NaAu species was also studied computationally at the CCSD(T) level with basis sets of increasing zeta quality thus allowing to evaluate the molecular parameters and the dissociation energy at the complete basis set limit.

The chemical bond between Au(I) and the noble gases. Comparative study of NgAuF and NgAu+ (Ng = Ar, Kr, Xe) by density functional and coupled cluster methods

The nature of the chemical bond between gold and the noble gases in the simplest prototype of Au(I) complexes (NgAuF and NgAu+, where Ng = Ar, Kr, Xe), has been theoretically investigated by state of art all-electron fully relativistic DC-CCSD(T) and DFT calculations with extended basis sets. The main properties of the molecules, including dipole moments and polarizabilities, have been computed and a detailed study of the electron density changes upon formation of the Ng-Au bond has been made. The Ar-Au dissociation energy is found to be nearly the same in both Argon compounds. It almost doubles along the NgAuF series and nearly triples in the corresponding NgAu+ series. The formation of the Ng-Au(I) bonds is accompanied by a large and very complex charge redistribution pattern which not only affects the outer valence region but reaches deep into the core-electron region. The charge transfer from the noble gas to Au taking place in the NgAu+ systems is largely reduced in the fluorides but the Ng-Au chemical bond in the latter systems is found to be tighter near the equilibrium distance. The density difference analysis shows, for all three noble gases, a qualitatively identical nature of the Ng-Au bond, characterized by the pronounced charge accumulation in the middle of the Ng-Au internuclear region which is typical of a covalent bond. This bonding density accumulation is more pronounced in the fluorides, where the Au-F bond is found to become more ionic, while the overall density deformation is more evident and less localized in the NgAu+ systems. Accurate density difference maps and charge-transfer curves help explain very subtle features of the chemistry of Au(I), including its peculiar preference for tight linear bicordination.