| dc.description.abstract | The use of density functional tight-binding (DFTB) in the theoretical studies of nanoclusters opened up access to longer timescales in simulation at an affordable computing cost and with little trade off in accuracy against ab initio or first principle methods. The purported global minimum (GM) structures of small Cu, Ag and Au clusters at the DFTB level, predicted by a modified basin-hopping global optimization algorithm, have revealed the existence of GM structures manifesting in chiral pairs Cu12 , Cu14 , Cu19 , Ag14 , Ag17 , Ag20 , Au10 , Au15 and Au18 . These chiral structures are studied by the Hausdorff chirality measure and ultra-fast shape recognition technique to ascertain their chiral nature in a mathematical formalism, in addition to an adroit and tandem use of both methods in identifying intermediate structures that point to suitable reaction coordinates derived from vectorial considerations to elucidate the enantiomeric transitions in Cu14 , Au10 and Au15 that are observable with a Brownian-type isothermal molecular dynamics simulation. Calculation of vibrational frequencies suggests the transition mechanisms are attributable to normal modes facilitating transitions between enantiomers via the identified intermediate structures. In the case of Au18 , where chiral states are hindered by hypothesized high energy barriers betweenthem, metadynamics has demonstrated its biasing abilities to overcome such barriers and shown the existence of transition pathways in an expressive lower dimension in the free energy landscape. In the second segment of this thesis, a systematic study of static neutral Aun structures in the range n = 3-20, using a recent DFTB parametrization available based on an adaptive scheme, is conducted to revisit the critical size, nc where the dimensionality transition of planar-nonplanar Au clusters occurs. The quality of said DFTB parametrization is assessed, and found to be adequate and consistent against structures reported in the literature. The energy landscapes of Aun close to nc explored by metadynamics are characterized by distinct regions of energy wells separated by barriers, and carry with them valuable information encompassing both the conformational enthalpy and conformational entropy of Au clusters. | en_US |