We have used a molecular dynamics technique to simulate the relationship between nanocluster precipitation and thermal conductivity in Si/Ge amorphous multilayer films, with and without Cu addition. In the study, the Green-Kubo equation was used to calculate thermal conductivity in these materials. Five specimens were prepared: Si/Ge layers, Si/(Ge + Cu) layers, (Si + Cu)/(Ge + Cu) layers, Si/Cu/Ge/Cu layers, and Si/Cu/Ge layers. The number of precipitated nanoclusters in these specimens, which is defined as the number of four-coordinate atoms, was counted along the lateral direction of the specimens. The observed results of precipitate formation were considered in relation to the thermal conductivity results. Enhancement of precipitation of nanoclusters by Cu addition, that is, densification of four-coordinate atoms, can prevent the increment of thermal conductivity. Cu dopant increases the thermal conductivity of these materials. Combining these two points, we concluded that Si/Cu/Ge is the best structure to improve the conversion efficiency of the Si/Ge amorphous multilayer films.

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The structural changes of irradiated Ni 3 Al were simulated by a molecular dynamics (MD) method. The irradiation event was modeled as the energy deposition of thermal energy produced by a high-energy ion beam, i.e. effective stopping power gSe. The L1 2 structure was taken as the initial structure and the effects of the irradiation event on the atomic structure were investigated. The relative degree of order, defined as the ratio of the calculated diffraction peaks of the L1 2 structure before and after the irradiation, and the number of site-exchanged atoms were calculated and found to show good correlation with gSe. The strength of the specimen was estimated from potential energy and it was decreased after the irradiation. Results of the uniaxial extension test done in the MD simulation suggest that the off-site atoms and site-exchanged atoms are the major cause of the reduction of specimen strength.