A Theoretical Investigation of Group 11 Halides
Abstract (Summary)Restricted Item. Print thesis available in the University of Auckland Library or available through Inter-Library Loan. A set of spectroscopic constants for the group 11 diatomic halides is presented, calculated using a variety of density functional and ab-initio methods. Selected structural, spectroscopie and energetic properties for the smaller MnXn (n=2-4) clusters of the group 11 are also calculated using the Becke-Perdew-Wang functional. Trends of properties and bonding are analysed. It is found that the diatiomic molecules are ionic, with properties that can be rationalised using electrostatic models. However they also possess a smaller amount of covalent bonding due to metal-ligand orbital overlap. The bond properties of the clusters are similar to those of the diatomics with the difference that the smaller clusters (dimmers) have metal-metal interactions. At the density functional level these interactions are not like metallophillic interactions and instead have properties that are intermediate to dative and ionic bonds. A study of the relative accuracy and errors of the pseudopotential method is performed by comparing some spectroscopic properties of AuH calculated using scalar all-electron and scalar pseudopotential methods. Estimates of the average errors for the relativistic pseudopotentials, with respect to the all-electron results, are 0.003 A for bond lengths and 0.05 eV for dissociation energies. Both errors are substantially less than the uncertainties due to basis set superposition errors and incompleteness. From this it is concluded that the use of pseudopotentials does not introduce any significant errors, when they are used in place of equivalent all electron methods. The structures of Cu3Cl3 and Cu4Cl4 are derived using gas electron diffraction and found to be in excellent agreement with the theoretical predictions. The dissociation energies of the gold halide diatomics are measured using ion cyclotron reaction experiments and also found to be in good agreement with experimental values. Theoretical predictions of the spectroscopic properties of the AuX+ diatomics are presented. Those of AuI+ compare well with the experimentally derived ionization potential and bond dissociation energy. A discussion of the differences between the properties of the cations and the neutrals is made. The experimental photo-electron detachment spectra of CuX-2 and AuX-2 are interpreted using DFT and ab-initio calculations. Good agreement is found for most assignments, with excellent agreement for the electron affinities. The theoretical structures and IR spectra of the neutrals, cation and anions are presented. The bonding in the AuX2 molecules is examined and it is suggested that gold in AuF2 is Au(II), one of the few examples of this oxidation state.
School Location:New Zealand
Source Type:Master's Thesis
Date of Publication:01/01/2001