| First principles molecular dynamics (FPMD) plays a significant role in computational material science, especially at atomic scale. In this thesis combined with newly-developed constant pressure molecular dynamics which is parameter-free, we studied the dynamical properties of carbon nanotube, silicon cluster under external pressure and found pressure induced structural transition. For hydrogen storage, we propose a graphite confinement mechanism which could be stable under certain pressure. In cluster structure calculation, by first principles method we predict cage-like structure of Au32-Ih structure will be stable under zero temperature calculation. This kind of structure was never been expected in metal elements. But in room condition, comparing with PES experiments we predict that quasi-cage structure with 3 inner atoms will be more stable due to vibrational entropy contribution. For larger gold cluster, we optimized the Au55-58 cluster and explain the mechanism of amorphization in such cluster. In the size range strong relativistic effect in gold will play a key roll and make gold structure different from Cu and Ag which have similar electronic configuration with Au. Besides nanosystem we also simulated AlSi alloy system by FPMD and found some possible liquid-liquid structural change.The thesis is structured as below: Chapter 1 is a general introduction about computational material science and nano science, Chapter 2 will give some brief description about the method we used, Chapter 3 is about the SWCNT under pressure and hydrogen storage in graphite, Chapter 4 is about constant pressure MD of Si cluster, Chapter 5 is about gold cluster study and Chapter 6 is about AlSi liquid simultion.
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