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Global minimum search of atomic and molecular clusters
My research is focused on the search for low-lying structures of atomic and molecular clusters and on the structural evolution of medium-sized atomic clusters (boron and gold). Since the properties of clusters are size dependent, a systematic study of structural evolution of clusters from small sizes is necessary. The theoretical methods used to study the structural evolution of medium sized clusters are based on global optimizations. Basin-hopping (BH) algorithm coupled with Density Functional Theory (DFT) and minima-hopping (MH) algorithm serves as satisfactory unbiased global search techniques to explore the potential energy surface (PES) of small and medium-sized clusters. The BH algorithm is particularly effective for systems such as B 18, Au17-, where the global minimum is easy to locate, while the MH algorithm is useful for more complex system such as water clusters. The combination of photoelectron spectroscopy followed by theoretical elucidation of structure is an important tool for studying small to medium-sized clusters as shown in case of gold and boron. The experimental photoelectron spectra are used to compare with the theoretically simulated spectra for the lowest energy clusters obtained from unbiased global search methods. This strategy helped us in identifying a new class of clusters, such as hollow cages of gold (Au16-, Au17-, Au18-) and smallest nanotube of boron (B20), which can be used as building blocks for new nanomaterials. ^ In case of complex systems such as water the strategy of using MD simulations to perturb coordinates through MH algorithm is useful because there exists a large number of low-lying/near-isoenergetic isomers, many of which have the same oxygen network (same structural family). New global minima are identified for (H2O)11 and (H2O)13 using MH algorithm.^
Bulusu, Satya S, "Global minimum search of atomic and molecular clusters" (2006). ETD collection for University of Nebraska - Lincoln. AAI3237486.