First Principle Study On Energy Application Of Metal Cluster

Clusters compose of several to several thousand of atoms, molecules or ions. Ithas the scale from several angstrum to several hundreds of angstrum, conbining togetherthrough physical or chemical interactions. Their characteristics are different from freeindividual atom or molecule, and also distinguish from liquid or solid state. Their potentialpromising application has attracted much attention on their forming physical andchemical characteristics. Broad application prospects have attracted much attention ontheir formation mechanism, physical and chemical properties and various potential applications.New energy source has become the focus of attention all around the world. Hydrogenstand out , in the development of new energy with its rich resources and high caloricvalue. How to safely and effectively store hydrogen is still the bottleneck area for itspractical application. Solar energy as primary energy, can be described as inexhaustible.The applications of solar energy has been improved from solar thermal conversion methodto photoelectric conversion nowadays. As examples of the photoelectric conversion solarcells have been focused on, while efficiency still can't meet the requirements of practicalapplication for using organic materials as photovoltaic solar cellOur jobs focus on discussing metal clusters'potential application in new energysource, taking the advange of metal clusters'unique physical and chemical characteristics.Our jobs include two parts.The study subject of the first part is the hydride aluminum. We discuss how to usenanomaterial based on metal clusters to store hydrogen and their advangeness, compared with solid state. Our calculations with DFT method present that the rich hydrogen syetemcan form Al_nH_3n cage cluster structures. In these structures, Al₆H₁₈ and Al₁₂H₃₆ structureswith O_h symmetry are most stable. The structure optimization of Al₁₂H_m (m = 12,14, 16, and 20 ) shows that the Al₁₂ cluster frame with Oh symmetry tends to adsorb morehydrogen atoms than that with Ih symmetry. The electronic characteristics of these clusters,including the diffrence between the highest occupation molecular orbital (HOMO)and the lowest unoccupation molecular (LUMO) orbital, binding energy, vertical electronaffinity and ionizaiton potential, represent the stability of Al₆H₁₈ and Al₁₂H₃₆ cage structuresfurtherly. Both the deformation of electron denstiy with the briged hydrgon atomsadded and the orbital energy level distribution show the interaction mechanism betweenthe hydrgon atoms and the aluminum atoms. The chain structures of Al₆H₁₈ and Al₁₂H₃₆clusters are optimized also. We notice that with the atom number increased, the hydridaluminum clusters tend to exit with cage structures. It is interesting that we find takingAl₁₂H₃₆ cage structure as basic unit, we can get stable (Al₁₂H₃₆)n chain structures. Theirbonding are similar to that of (AlH₃)_n chain structure. Our findings provide a new attemptto hydrogen storage. At the same time, Both the formation heat and combusion heat ofAl₁₂H₃₆ show that it is a promising high-energy high-density material (HEDM).The second part of our jobs focus on studying the plasmon formation in one dimensiongold chaines. In gold atom with the 5d electron less shielded by s and p subshells,relativistic effects become a far more important factor affecting electronic properties. Thehybridization of d electrons and s electrons decreased the gap between molecular orbitalscomposed of d electrons and that of s electrons, which makes it possible for d electronsto participate in the low energy exciation processes. the presence of d electrons affect theplasmon formation greatly. It is well known that d electrons are very localized, whichresults in the transverse mode from pi orbitals composed of d electron having very lowassociated transition momnets. Because of the defect of TDDFT method in frequencydomain, our calculated excitation energies are less than 5 eV. In this energy range, novisible transverse modes are observed. The same kind of excitation involving p electronsis expected to have much high excitation energy out of our calculation range. An approximatespectrum within a frozen orbital picture at lower computation are used to prove ourjudgement. We use one dimension gold chain with nine gold atoms to discuss the effect of gold lines on the absorption spectrum of polymer hexylthiophene (P3HT). The blendof P3HT and PCBM are an important of solar cell material. It is the excitation of theÏ€-orbit electron in the P3HT that gives the photovoltaic effect in the blend. We find that theabsorption spectrum of the dimer and tetramer of hexylthiophene shift from ultra violetregion to visible and infrared region with the gold chain added. This helps us to use theradition of solar energy effectively.