Size-selected, ligand-free gold clusters with diameters less than 2 nm can be routinely generated in the gas phase. The pronounced size dependence of their physical and chemical properties is one of their most important features. In principle, quantum-chemical methods allow many properties of small gold clusters to be predicted with high accuracy. However, for larger clusters, the large number of possible isomers makes extremely difficult the search for a global energy minimum. Often, only a small set of the possible structures can be considered, without any guarantee that the global minimum is included in the set. the structures of small gold cluster anions and cations with up to 13 atoms have been inferred through a comparison of theoretical and experimental collision cross sections from ionmobility measurements as well as far infra red photo diosciation techniques FIR-MPD. A remarkable finding in this study was that the 2D-3D structural transition for Aun occurs at cluster sizes of around n=11 and 12 atoms. This result was later confirmed through a comparison of photoelectron spectroscopy (PES) data with calculated density of states (DOS) curves. For Aun with n=16–18 and 21–24, experimental and theoretical evidence for hollow It has been suggested, on the basis of quantum-chemical calculations, that medium-sized gold clusters, such as Aun with n=32–35, and 50, also may have cage-like structures. In contrast, in a recent study, Au32 was assigned an amorphous, but dense, structure on the basis of a comparison of data from PES and the calculated DOS. Lowsymmetry “disordered” structures have also been also proposed for Au28 and Au55. These results were supported by a combined PES and theoretical study which excluded symmetric structures for Au55. This highly studied subject is the perfect scenario in which we want to introduce a new Genetic Alogitum code capable of finding the global structures already known as a test and bench mark study and elucidate those who have not been correctly identified . We also study the revealing genalogy of each cluster involved in this study. This with the aim not only to obtain the global minima but also in understanding how nanoclusters transform from one structural type to another as a function of size, which we believe it is a critical issue in cluster science. Here we report new and unreported lowest energy structures and higher energy isomers involved in the structural geometry transition for gold Au4 through Au30. The study has been done for neutral as well as charged clusters. We show and discuss their density of states, their IR spectra, their binding energies and their vertical and detachmente energies which we compare with the available experimental data. This results have been obtained by means of MEGA, the Mexican Enhanced Genetic Algorithm which is Genetic Algorithm-DFT methodology. The current study allows the detailed structural evolution and growth routes from the hollow cages to more compact structures to be understood and provides information about the structure-function relationship of these clusters, some of which have been wrongly identifyed in previous years.
